HHBBMMMI INTRODUCTION! TO BOTANY UNIVERSITY OF CALIFORNIA DEPARTMENT OF EDUCATION GIFT OF THE PUBLISHER No. Vetoed / ? 3 , LIBRARY OF THE UNIVERSITY OF CALIFORNIA. GIFT OF BIOLOGY LIBRARY G Class INTRODUCTION TO BOTANY BY WILLIAM CHASE STEVENS \\ PROFESSOR OF BOTANY IN THE UNIVERSITY OF KANSAS BOSTON, U.S.A. D. C. HEATH & CO., PUBLISHERS 1902 BIOLOGY LIBRARY G COPYRIGHT, 1902, BY D. C. HEATH & Co. PRINTED IN UNITED STATES OF AMERICA PREFACE. ENOUGH work has been outlined in this book for a year's course in those schools that are prepared, by suitable time allotted to the subject and by laboratory equipment, to do comprehensive and thorough work. A term could be devoted to the work outlined in Chapters I to X inclusive ; and where the daily laboratory periods are one hour or less, the entire school year could be profitably occupied by the course there outlined. It is, of course, presumed that the teacher will select from the book such work as the possibilities of his school warrant. It is not expected that each student will perform all of the physiological experiments herein outlined ; but different experiments are to be assigned to individuals or groups of students, the results to be used for purpose of demonstration before the entire class. Much stress is laid on laboratory work, which is to be done with the utmost possible care and accuracy, not only that the student may respect his work and that the knowledge gained may be exact, but also that the fine opportunity which the study of plants so richly affords for training in seeing and interpreting facts, may not be passed by. In the discussion following each set of laboratory direc- tions it is inevitable that results which the student is expected to work out for himself are sometimes told ; but 22lf46 iv Preface. there is a large body of work for which no such aid is given, quite sufficient for training in independent and self-reliant study. In order that the student may not be hampered with preconceptions of what he is expected to see and to repre- sent, in choosing the illustrations care has been exercised to avoid in most instances those subjects which he is required to * draw in his laboratory book. And that the main facts about the nature of plants may be kept plainly before the student, glossology has for the most part been kept from the discussions and placed in compact form in Part III. I wish to acknowledge my special indebtedness to my colleague, Professor M. A. Barber, in conjunction with whom a large part of the course here outlined has been worked out. He has read most of the manuscript and has made many helpful suggestions. The manuscript has been examined by Dr. C. E. Mc- Clung, Associate Professor of Zoology, University of Kansas; Dr. V. M. Spalding, Professor of Botany, Uni- versity of Michigan; Dr. John W. Harshberger, Instructor in Botany, University of Pennsylvania; Dr. Rodney H. True, Plant Physiologist, Department of Agriculture, Washington, D.C. ; Mr. L. Murbach, Central High School, Detroit, Michigan; Principal Maurice Ricker, High School, Burlington, Iowa. The proof has been read by Dr. D. M. Mottier, Pro- fessor of Botany, University of Indiana; Dr. Charles H. Clark, Phillips Academy, Exeter, New Hampshire ; Dr. F. C. Newcombe, Junior Professor of Botany, University of Michigan ; B. M. Stigall, Instructor in Biology, Manual Training High School, Kansas City, Missouri. Dr. E. C. Franklin, Professor of Physical Chemistry, Preface. v University of Kansas, has revised the paragraphs dealing with the nature of diffusion and osmosis. Dr. S. W. Wil- liston, Professor of Paleontology, University of Chicago, has read the chapter on Plants of Past Ages ; S. J. Hunter, Associate Professor of Comparative Zoology, University of Kansas, has read those portions of Chapter VIII deal- ing with the anatomy of insects; M. W. Sterling, Associate Professor of Greek, University of Kansas, has revised and contributed to the etymology of terms in the glossary and flora; Dr. W. H. Carruth, Professor of German, Univer- sity of Kansas, has revised the passages translated from Sprengel. To all of these teachers I wish to express my grateful sense of obligation for suggestions leading to the better- ment of the book. The illustrations have been made by Miss Marguerite Wise, Instructor in Botany and Zoology, University of Kansas, Mr. Sidney Prentice, Miss Luella Pugh, and Miss Katherine Crew. I wish to acknowledge my special in- debtedness to Miss Wise, whose knowledge of the subject has greatly lightened the task of preparing the illustra- tions. She has made all of the wash drawings excepting Fig. 192, which is by Miss Crew. Of the original line drawings, Mr. Prentice made Figs. 10, 19, 21, 37, 45, 47, 48, 93, 1 80, 198, 199, 201, 202, 203, 204. The remainder of the original illustrations and most of the copied figures were done by Miss Wise. W. C. S. UNIVERSITY OF KANSAS. CONTENTS. PART I. MORPHOLOGY, PHYSIOLOGY, AND ECOLOGY. CHAPTER PAGE I. LABORATORY WORK i II. SEEDS AND SEEDLINGS 5 III. ROOTS 28 IV. BUDS AND STEMS . . . . . - 45 V. LEAVES 75 VI. GROWTH AND MOVEMENT 100 VII. MODIFIED PARTS 134 VIII. FLOWERS 147 IX. DISPERSION OF FRUITS AND SEEDS .... 207 X. STUDIES OF SELECTED SPERMATOPHYTES . . .218 XI. SLIME MOULDS, BACTERIA, AND YEASTS . . .251 XII. ALG.E, FUNGI, AND LICHENS 264 XIII. MOSSES, FERNS, AND HORSETAILS .... 286 XIV. ADAPTATION TO ENVIRONMENT . . . . . 303 XV. PLANTS OF DIFFERENT REGIONS . . . .328 XVI. PLANTS OF PAST AGES 351 XVII. CLASSIFICATION OF PLANTS . 359 viii Contents. PART II. THE HERBARIUM, LABORATORY EQUIPMENT, AND PROCESSES. CHAPTER PAGE XVIII. THE SCHOOL HERBARIUM . . . . . 367 XIX. LABORATORY EQUIPMENT 371 XX. REAGENTS AND PROCESSES 381 PART III. GLOSSOLOGY. GLOSSARY 399 INDEX TO PARTS I AND II 429 INTRODUCTION TO BOTANY. CHAPTER I. LABORATORY WORK. 1. Method of Study. The study of plants, to be of much value, requires accurate observation. This is best secured by a definite and orderly record, by the student, of what he has seen. Simple drawings are usually more effective than a verbal description, and are therefore much used ; r fV> e work here outlined. Students unskilled in drawing ne,t rot be discouraged by this requirement, for after som<: nn) of persistent and patient effort the number of thuse who cannot achieve passably good results is few indeed. The drawings furnish the best possible mode of expression in the study of form and structure, for they show briefly and positi ely how well the student has observed. It is best, as a rule, not to point out the faults of the draw- ings to the studer^- but to have him detect them, which he rarely fails to b. ole to do when asked where the faults lie. The drawin , should be very simple, but never merely sketchy. Every line should have a meaning and should clearly indicate what it is intended to show. Only outlines are desired ; shading is unnecessary, and should not be attempted except by one who thoroughly understands its application. : : 2 Introduction to Botany. There are three simple rules which the student should keep in mind, (i) The drawings should be on a suffi- ciently large scale to allow the smallest details to be put in without crowding. (2) All parts must be in correct pro- portion with reference to one another and in right relative positions. (3) Some one dimension of the object should always be used as a measuring rod in establishing the lengths of the others. If these rules are followed, much subsequent correction will be avoided. A very serviceable notebook for the notes and drawings is afforded by the No. 2 double and reversible note covers, opening at the side, filled with a good quality of unruled linen ledger paper. 1 The drawings should be symmetrically disposed over the sheet without crowding, as shown in Fig. 74. They should be made with a 6 H drawing pencil kept quite sharp by rubbing it occasionally with a longitudinal to-and- fro motion on a piece of No. o emery cloth or sandpaper. Neither a soft nor a dull pencil should ever be used. The descriptive notes, written in ink, should be on a separate sheet facing the drawings, the parts of which are to be lettered and referred to in the notes accordingly. Notes written with a pencil are liable to smirch the drawings and must not be tolerated. The student should strive for the utmost accuracy and neatness in the drawings and notes ; he should have a personal pride in them, for they repre- sent his capabilities in seeing and interpreting facts with which he has personally to deal. 2. Procedure in Drawing. After having determined the proper scale of the drawing, that is, whether its diameters should be twice as great, three times as great, etc., as those of the object, place points to establish the limits of the 1 Made by.(?h^3 f W. Sever & : Cp.,: Cambridge, Mass. Laboratory Work. 3 long and short diameters, using the short diameter, for instance, as a measuring rod ; and then with a very light touch of the pencil, making a barely visible line, draw the outline. If the form is not right at the first attempt, correct it before rubbing out the false line, for the latter may serve as a guide in correcting the error. When the form has been satisfactorily drawn, rub out the false lines once for all, and retrace the final outline with a firm touch so that it stands out sharply, but the pressure of the pencil must not be hard enough to dig into the paper. Colored pencils are very helpful for giving distinct tints to the different parts of a drawing, but they should be used only where a definite purpose is to be served, as in calling attention to homologous parts in different drawings. The coloring should be done with very light cross-hatching strokes until an even light tint is produced. If satisfactory results are not obtained in this way, the color can be dis- tributed more evenly by rubbing over the colored areas with a paper or chamois stump used by artists in crayon shading. 3. The Student at Work. The student should think of his work as he proceeds. The drawings and notes are in- tended to assist him in gaining a clear conception of the problems before him, and they are good evidence of his success or failure ; but he should possess his subject more completely than the drawings and notes may show. The laboratory is so much limited space in which certain con- veniences for work are provided. Were it not for these conveniences, it would be better to study the subjects out of doors in their natural surroundings. The student who thinks as he works associates the subject with the natural conditions, and sees the bearing of what he is learning in the laboratory on the life of plants as they occur in nature. 4 Introduction to Botany. The student should never ask the teacher questions which with reasonable effort he can answer for himself ; as questions arise, he should continually recur to the sub- ject of his study as the most reliable source of information about itself. It is a good plan, when pertinent questions are asked, to write them on the blackboard for the class to consider, and finally to use them as topics for a general discussion. 4. Field Work. The laboratory work should, of course, be supplemented by field work. The locality where the work is to be carried on should first be visited in order to determine what the students can best learn there ; then questions and directions should be written on the black- board for the student to copy, in order that his work may have definiteness and meaning. Drawings and notes which are to count as an essential part of the course should be required in this work. In succeeding chapters, problems are given which are to be worked out in the field, but they will need to be supplemented by others particu- larly adapted to the specific locality. CHAPTER II. SEEDS AND SEEDLINGS. PROVIDING MATERIALS. It is a simple matter to provide the seeds required for the work of this chapter, but there may be some difficulty in growing the seedlings on account of lack of space and equipment. If a greenhouse cannot be used, some arrangement must be made for growing the seedlings in a warm room. Boxes should be made not more than six inches deep, and white pine sawdust, or chopped sphagnum when obtainable, should be placed in these to a depth of four inches. If the classes are large and the space which can be devoted to seed boxes very limited, they may be placed one above another in tiers separated by a space of about ten inches. Moisten the sawdust throughout and then plant the seeds to a depth of about one inch in rows between two and three inches apart. After covering the seeds, press the sawdust down firmly with the palm of the hand or with a wooden block. The seeds will germi- nate more quickly if soaked in water over night before planting. The first sowings should be made about two weeks before the work is to begin, and then other sowings of the same kinds of seeds at intervals of a few days, in order that plenty of seedlings may be on hand in dif- ferent stages of germination. The seeds need to be kept warn,! and well watered, but it is not necessary that they should have light until they have germinated ; after that time the seedlings will grow weak and spindling if too much shaded. OBSERVATIONS ON SEEDS AND SEEDLINGS. Lima Bean. i. Make drawings of the external appearance of a dry bean from the two most important points of view, showing all structural characteristics. Make drawings to the scale, 5 6 Introduction to Botany. x 1.5 ; that is, the diameters of the drawings are to be 1.5 times as great as the corresponding diameters of the bean. The two most important points of view are those which best show the form of the bean, and the structures which may have some significance in the formation or germina- tion of the seed. If beans in the pod, preserved in 2% formalin, or in 70% alcohol, are available, the data for judgment will be more complete. Compare with the dry bean one which has been soaked in water over night, and note any difference in size, form, and texture. 2. Slip the skin or seed-coats (there are usually two seed-coats, the outer, termed the testa, being thicker and harder than the inner) carefully from a soaked seed, notic- ing whether it is attached to the rest of the seed at any point, or simply lies in contact with it. Can any structures be seen after the seed-coats are removed which could not be seen before ? If so, make drawings from the two points of view which will most clearly show them. Is there any connection between structures which are removed with the seed-coats and those lying beneath them ? How do the dry and soaked seed-coats of the bean differ as to hardness and toughness ? What significance do you see in the differ- ence ? In what ways is the seed protected against injury ? Answer these questions in the notes, and refer to the draw- ings wherever they will illustrate what is said. 3. After the seed-coats have been removed, note whether the two halves of the bean, termed cotyledons, are united at any point; then carefully separate the cotyledons and place them on the table, convex side down, and in contact, at the right point, with any part from which they may have been severed. Draw as thus seen on the same scale as before. 4. Study with a lens the structures which were revealed Seeds and Seedlings. 7 by separating the cotyledons, and draw to a scale suffi- ciently large to bring out the details thus observed, say, x 4. If any parts are folded together, make drawings to show their relationship clearly. The student should not be satisfied with his work until the drawings show the facts as clearly as he can see them by a thoughtful examination of the object. Germinating Lima Bean. 5. Make drawings of a bean in the first stages of germi- nation, and in various succeeding stages, identifying the parts already studied in the ungerminated seeds. Note any new structures. 6. The following terms should now be applied in the notes to the structures designated by them : The scar where the seed was attached to the pod is called the hilum. The rudimentary plant formed in the seed is called the embryo. The first leaves of the embryo are called the cotyle- dons. The bud sometimes present between the cotyledons is called the plumule. The small stem in the seed from which the cotyledons grow is called the caulicle. The first root produced as a continuation of the caulicle is called the radicle. All of the embryo below the insertion of the cotyledons is called the hypocotyl (including caulicle and radicle). All of the embryo above the insertion of the cotyledons is called the epicotyl. The opening in the seed-coats near the tip of the caulicle is called the micropyle. 8 Introduction to Botany. 7. After the drawings have been pronounced satisfactory by the instructor, impart different tints to the separate structures by means of colored pencils, using the same colors for the corresponding parts in the germinated and ungerminated seeds. Thus : color the cotyledons yellow, the plumule and whatever develops from it green, the cau- licle orange, the radicle and succeeding roots red, reserve food outside of the embryo blue, and when the cotyledons contain reserve food dot their yellow color with blue. 8. In the germinating Lima bean, what structures grow most rapidly at first ? Can you see any physiological reason why one structure should develop before another ? How does the seedling manage to rise through the soil into the light and air ? 9. Make a cross section of the main root where a whorl of rootlets arises, and show by a drawing the method of origin of the rootlets. What advantage do you see in the disposition of the rootlets in a regular order around the main root ? 10. Follow the behavior of the cotyledons, and try in this way to determine their functions. In your judgment, at what stage does the process of germination cease ? 11. After two or more sets of leaves have developed, make drawings to show their position on the stem with reference to the next higher or lower set. What signifi- cance do you see in a regular arrangement of the leaves ? 12. Examine the terminal bud of the seedling with a lens and determine what structures develop from it. Castor Bean. 13. Make drawings of the external appearance of a castor bean from the two most important points of view. Scale, x 2. Seeds and Seedlings. 9 14. Carefully remove the shell or testa from a seed and note any structural details thus brought to light. Split the shelled seed longitudinally through its greater diameter, and make drawings of the internal structures. Split another shelled seed longitudinally through its lesser diameter, taking care to cut the structures already dis- covered exactly through the middle. Make a 'drawing from this point of view, sharply demarking the limits of the different structures. Make a cross section of a shelled seed a little below the middle, and draw the cut surface, bringing out clearly the outlines of the different parts. These drawings should all be made to the scale, x 3. Germinating Castor Bean. 15. Draw the castor bean in the first stages of germina- tion, showing how the seedling protrudes through the shell. Scale, x 2. 1 6. Remove the testa from a seed in the first stages of germination, and split it in halves longitudinally through the broad diameter. Draw from the point of view of the interior surface. Scale, x 3. Split another seed in the same stage of germination longitudinally through the nar- row diameter, taking care to halve all of the structures, and draw from the cut surface to the same scale. 17. Treat, in a similar manner, seedlings in later stages of germination, and call attention to any new structures which were not seen in the ungerminated seed. Follow the changes which the different parts undergo up to the stage where all reserve food materials have been used up. 1 8. In your notes, answer briefly the following ques- tions : Where and how does the seedling crack the hard shell ? How does the seedling get above the soil ? How does the young plant get the food materials which are lo introduction to Botany. stored up for its use in germination ? How does it differ from the embryo of the Lima bean in this respect ? Com- pare the means of protection possessed by the seed of the castor bean with that of the Lima bean. Indian Corn. 19. Make drawings of the exterior appearance of a grain of Indian corn, from the two points of view which you consider the most important. Scale, x 2. 20. Remove the skin from a soaked grain, and if any new structures are revealed, draw to the same scale. In this instance and in all grains the wall of the ovary in which the seed is formed constitutes a part of the skin. 21. Carefully dissect out the central structures from a soaked grain and draw from the two most instructive points of view to the scale, x 3. 22. With a sharp knife, make cross sections of the inner structures on either side of the center, about halfway toward each apex. Examine with a lens, and draw to a scale large enough to show all that the lens has revealed. 23. Halve a soaked grain longitudinally through the lesser diameter, making a sliding cut with a sharp knife so as to secure smooth surfaces. If the knife does not pass through the middle of the structures, carefully trim the larger piece until an exactly central section is secured. Draw the cut surface. Scale, x 3. Place a drop of iodine solution on the cut surface, and after a minute draw it off with filter paper. The iodine will color the starchy parts of the seed a deep purple. Germinating Indian Corn. 24. Make drawings of the external appearance of germinating Indian corn in successive stages of develop- ment. Scale, x 1.5. Seeds and Seedlings. 1 1 25. Make a median longitudinal section through the lesser diameter of seedlings in various stages of germina- tion, and draw from the point of view of the cut surfaces. The drawings should show definitely the changes which the several parts undergo as germination progresses. 26. Make cross sections of the stem of a well-advanced seedling, and drawings to show how the leaves are wrapped together, as shown by these sections. 27. What are the differences in the details of growth of Lima bean, castor bean, and Indian corn which result in the grain of corn remaining below the ground in germina- tion, while, in the beans, the bulk of the seed is lifted above the ground ? By what means does the corn seed- ling obtain the food which is stored in the seed ? 28. After the instructor has pronounced the drawings of castor bean and Indian corn satisfactory, tint the dif- ferent structures with the colored pencils, as in the case of the Lima bean, using the same color for the correspond- ing parts in all of the seeds and seedlings studied. General Comparisons. 29. Make drawings on one page, for comparison, of the seeds of Lima bean, castor bean, and Indian corn, select- ing the point of view which best shows the different structures, and with the colored pencils give the same colors to the corresponding parts. 30. In your notes briefly compare the corresponding parts of the seeds studied. Experiments. 31. With the sharp point of a penknife, scrape up a small portion from the cotyledon of a soaked Lima bean and mount in a drop of iodine solution (see page 387), on a glass slip, and cover with a coverglass. Examine with 12 Introduction to Botany. a compound microscope, using a | or J inch objective. Starch grains will be seen of various shades of purple, depending on the degree of action of the iodine ; while other granules, whose substance, called proteid, is closely related chemically to the white of an egg, will appear from yellow to brown. These are the two chief classes of reserve food in the seed of Lima bean. The fact that starch is present in large quantities is manifest by the deep purple color which appears when a piece of cotyledon is placed in a drop of iodine. A compound microscope would therefore not be necessary to demonstrate the mere presence of starch. 32. Mount in a drop of iodine, as before, scrapings from the cut surface of soaked Indian corn, and note the presence of both starch and proteid. 33. Treat in a similar manner some scrapings from the reserve food materials of castor bean. The regular brown bodies are proteid, while the irregular yellow or brown bodies and circular masses of varying sizes are castor oil. 34. Boil in Fehling's solution (see page 385) in a test tube a dry crushed seed of Lima bean, and note whether the presence of glucose is demonstrated by the production of a red precipitate of cuprous oxide. Treat in a similar manner a seedling which is somewhat advanced in germi- nation, and seeds and seedlings of castor bean and Indian corn. State in your notes your deductions as to the changes which the reserve materials in seeds undergo in the process of germination. 35. Place moist white pine sawdust to the depth of about an inch in four wide-mouth bottles. 1 Put several grains of Indian corn that have lain in water over night into two of these. Cover the corn with about 1 Such as No. 2750 in the catalogue of Whitall, Tatum, & Co., Philadelphia. Seeds and Seedlings. 13 half an inch of the moist sawdust, and press down firmly. Cork the four bottles tightly (two containing the seeds in moist sawdust, and two containing sawdust only) and leave over night in a warm place. The following day fasten a piece of tallow 'candle or wax taper to a wire handle ; light the candle ; remove the cork from one of the bottles con- taining sawdust only, and slowly lower the lighted candle into the bottle until it rests upon the sawdust. Leave the candle in this position for some time, and note whether there is a tendency for the flame to become extinguished. Remove the cork from one of the bottles containing the seeds and lower the lighted candle into it. If the seeds have been germinating properly, the flame will quickly expire. What do you conclude from these observations ? 36. Prepare limewater as described on page 387 ; pour some of the clear liquid into a clean, wide-mouth bottle ; then remove the cork from the remaining bottle of seeds, and, holding the mouth of the bottle close down over the mouth of the bottle of limewater, pour the gas from the bottle of seeds (as if pouring water) into the bottle of lime- water. Cork the bottle of limewater tightly and shake vigorously. The white precipitate of calcium carbonate now appearing in the water has resulted from the reaction between the carbon dioxide gas from the bottle of seeds, and the calcium hydrate of the limewater. See whether the air in the second bottle containing sawdust only gives a like result. Shake up some limewater in a bottle contain- ing only ordinary atmosphere, to see whether the precipi- tate is really produced by the gas poured from the bottle of seeds. 37. To demonstrate the identity between the gas given off by germinating seeds and a gas produced by a burning candle, or by breathing, perform the following experi- 14 Introduction to Botany. ments : Hold a lighted candle in the mouth of an inverted bottle until the candle is extinguished. Cork the bottle, set it right side up, and give the gas in it time to cool. Then pour limewater into the bottle and shake vigorously. The white precipitate will be produced as before. Blow the breath through a straw or glass tube into another bot- tle of limewater, holding the tube close to the bottom so that the breath will bubble through the limewater. After this process has continued for a short time the white pre- cipitate of calcium carbonate will be observed. 38. It would seem from these results that a chemical process takes place in germinating seeds similar to that which occurs in our breathing, or in the burning of a candle. It will be interesting to note whether this process is asso- ciated with visible changes in the reserve food supply in the seed. Scrape a small portion from the reserve food of a soaked grain of corn, and mount under a coverglass in a drop of water; examine with a high power. Treat in a like manner some of the remnant of reserve material still remaining in the grain attached to a far-advanced seedling. The starch grains in the latter preparation show erosions like those shown in Fig. 3, page 21. 39. To estimate the value of the reserve materials in seeds to resumption of growth of the embryo, perform the following experiments : Plant seeds of Lima bean in saw- dust, chopped sphagnum, or other suitable seed bed, and after the young plants appear, remove the cotyledons from some of them, and leave others in their normal condition. Compare the rate of growth of the two sets of seedlings. Soak grains of corn in water over night, and remove the outer food supply down to the fleshy cotyledon. Plant both depleted and normal grains in moist s. ^nd note their relative rates of growth. Try a similar ex t " ^^ f Seeds and Seedlings. 15 with Lima beans, removing the cotyledons from soaked seeds, and planting the much diminished embryos, together with normal seeds, in moist sawdust. Make comparisons of the results of all of the experiments of this kind, and write out your conclusions in full. This experiment will be more certain to succeed if the sawdust has been boiled, to destroy moulds and bacteria. 40. Soak seeds of barley in water over night, and plant in moist sawdust in a wide-mouth bottle ; place in the bottle a test tube containing a strong solution of pyrogallic acid and caustic potash ; cork the bottle tightly by shov- ing the cork to a short distance below the rim of the bottle and filling in over the cork with melted sealing wax. Prepare another set of seeds in the same way, but with a potash solution only in the test tube. The pyro- gallic acid in its alkaline solution absorbs the oxygen from the atmosphere in the bottle, while the caustic potash in both instances absorbs the carbon dioxide of the atmos- phere, and that which is produced by the germination of the seeds ; the conditions are, then, as follows : one bottle lacks oxygen and carbon dioxide, while the other lacks only the carbon dioxide. The experiment is designed to answer the question whether oxygen is necessary to germination. Let the experiment continue for several days, keeping the bottles in a dark and warm place. Record the results of your observations. 41. Remove the glass front and the hands from a cheap alarm clock. Provide a soft pine block about an inch square, whittle one end to a taper, and drill a small hole into it, so that it will slip through the opening of the dial face and tightly over the hour-hand spindle. Fasten a Petri 1 dish to y ~. : e outer face of the pine block by a melted 1 See catalogues of dealers in bacteriological supplies. 1 6 Introduction to Botany. mixture of one third beeswax and two thirds rosin, taking care to center the dish with the hour-hand spindle. Pack moist pine sawdust into the dish, level with the surface, and press soaked grains of corn into the sawdust, not very tightly, broad face down, but do not cover them with the sawdust. Put on the cover of the Petri dish, and hold it in position by means of clips made of spring brass wire. (See Figs. 7 and 8.) Wind the clock and set it in its nor- mal position ; that is, with the hour-hand spindle horizontal. Prepare seeds in another dish in exactly the same manner, but fasten it so that it will stand vertically on its edge. In the first experiment the directive effect of gravity will be neutralized by the revolution of the dish, while in the second, gravity may exercise its usual influence on the direction taken by root and shoot. Since the seeds are not covered by the sawdust, their progress in germination may be observed at any time without interrupting the experiment. The position occupied by the parts of the seedlings can easily be recorded for any period, by tracing with ink on the cover immediately over them. DISCUSSION. 5. Nature and Purpose of Seeds. A seed is essentially a young plant produced sexually by a flower (see page 168). The young plant has temporarily ceased to grow, and has been, or is to be, cast off from the parent plant, having first been provided with reserve food materials necessary to the resumption of growth, and with certain means of protection. The purpose of the seed is to insure the continuation, multiplication, and locomotion or distribution of the species. Many plants are too tender to survive the cold of winter, or the dry seasons of those regions where the rain does not fall for many months of Seeds and Seedlings. 17 the year. But the dry seeds of these plants can withstand great extremes of heat and cold, and do not need water to keep them alive ; indeed, the ability of seeds to survive adverse seasons is due in large measure to the small amount of water which they contain. Since seeds as a rule retain their vitality for several years, in some cases, indeed, for twenty-five or even fifty years, they can, if necessary, tide a species over one or more years which are unfavorable to growth. 6. Multiplication by Seeds. A single plant of Indian corn produces on the average about 130 grains of corn, which, under the favorable conditions resulting from culti- vation, might in the succeeding season give rise to 16,900 grains. An example of this kind will serve to demon- strate the immense capacity of multiplication by means of seeds ; although under natural conditions only a small portion of the seeds produced ever result in mature plants. 7. Migration by Seeds. Since land plants must draw their water and some other raw food materials from the soil, it is of great advantage, and even necessary, for them to be fixed in the soil by means of their roots. While the individual is thus anchored, the species is still able to move from place to place by means of the seeds. In this way, species have migrated through the long geological periods from regions which were becoming unhabitable to others which were more favorable ; and by this means the borders of continents which are rising from the oceans, and newly formed volcanic or coral islands, become colonized by plants from greater or less distances. It is a matter of common observation that tracts of land which have been protected from grazing animals become inhabited in the course of a few years by plants which were never seen 1 8 Introduction to Botany. there before ; and that treeless areas along the borders of streams soon become overgrown with dense groves of cottonwood and willow saplings after cattle are excluded, the seeds in some instances having come several miles from the homes of their ancestors. 8. Food and Protection. In order fully to understand the significance of the various structures of a seed, we must keep in mind its functions of continuance, migration, and multiplication, and the conditions under which these func- tions must be performed. It is of great importance that the young plant in the seed be protected against unfriendly contingencies. We find that mechanical injuries are pre- vented either by the extreme hardness of the embryo and reserve food, as in the case of Lima bean and Indian corn ; or, if the embryo and reserve food are oily and soft, by a covering of stony hardness, such as the castor bean and various nuts possess. The reserve food materials are packed tightly into the seed, and in a form which is, for the most part, insoluble in water, and on that account more certain of preservation within the seed. In some seeds the reserve material is stored entirely within the embryo, as in Lima bean ; in others it is partly within and partly without the embryo, as in Indian corn ; while in others, such as the castor bean, it lies wholly out- side the embryo. But this variation in the location of the re- serve food seems to have little significance so far as concerns germination, for in all cases it is finally transferred to the growing parts of the seedling ; and whether this takes place before the seed is cast from the parent plant, or only during the stages of germination, is apparently indifferent to the well-being of the young plant. The facts of significance are, that the embryo plant is alive, although in a tempo- rary state of inactivity ; that it has a sufficient store of Seeds and Seedlings. food materials locked in against loss ; and that the plant is not inclined to spring into activity, nor are the reserve materials liable to become unlocked except in the right season and under the proper conditions for the establish- ment of the young plant as an independent individual, FIG. i. Germination of the Mangrove. /, longitudinal section of the Mangrove flower; y, the fruit ; K, the seed germinating while yet contained in the fruit hanging to the tree (compare //) ; L, longitudinal section of the fruit showing the seedling separating from it ; H, branch of the Mangrove with seedlings pendent from it and others that have fallen and taken root in the moist soil. After K.ERNER. with its roots in the soil, and its leaves spread out in the sunlight and air. 9. Time of Germination. Some seeds are capable of germination as soon as mature, and even before they are cast off from the parent plant. One may sometimes see wheat germinating in the standing ears before harvest. 2O Introduction to Botany. The mangrove is a notable example of a plant whose seeds habitually pass through the first stages of germina- tion before falling from the tree (see Fig. i). In most cases, however, the seeds must go through a greater or less period of rest before they are in a condition for ger- mination ; and during this period of comparative inactivity, ferments are possibly being formed which are necessary to render the starches, oils, and some forms of proteid soluble in the cell sap. 10. Conditions Necessary to Ger- mination. Until the internal con- ditions are favorable through the formation of ferments, etc., the seed cannot germinate, but cer- tain external conditions are also necessary to germination. These are the presence of oxygen, water, a certain degree of heat. While some seeds have been known to germinate at tempera- tures quite close to the freezing point, most seeds germinate best between 16 and 27 C. (60.8 and 80.6 F.). This sig- nifies that until a certain amount of energy in the form of heat is afforded to seeds from the outside, some of the necessary processes attending growth cannot be initiated. Neither can germination begin until the seed has absorbed sufficient water to stretch its tissues and act as the solvent for its reserve food materials. Some seeds are able to absorb water until their tissues are stretched by a force equal to about 200 pounds per square inch ; and it is this stretching force which starts the increase in size of the embryo plant. If oxygen is excluded from seeds, they will FIG. 2. Photomicrograph of Starch Grains and in a section of a grain of Indian corn. Highly magnified. Seeds and Seedlings. 21 not germinate, although all other conditions are favorable. The oxygen serves a double purpose in helping to form new soluble and diffusible compounds from the reserve materials, and in sustaining the respiration of the embryo as it becomes quickened into renewed growth. The neces- sity of oxygen to germination has been demonstrated by Experiment 40, page 15, but it is also frequently demon- strated in nature by the fact that most seeds will not germinate in a water-soaked soil ; notable exceptions are the seeds of some water plants, such as those of Nelumbo, which are able to obtain sufficient oxygen from the water. 11. Digestive Ferments. The FIG insoluble and poorly diffusible , * "Photo micrograph or Starch Grams reserve materials are rendered from a grain of Indian com in soluble and diffusible by means an advanced sta s e of s ermina - * tion. of ferments present in the seeds. The ferment which attacks starch is known as diastase. The result of its work can be seen by a comparison of Figs. 2 and 3, which are photomicrographs of starch grains from ungerminated and germinating seeds of Indian corn. In Fig. 3 it is seen that the grains have been much eroded around the border and throughout their whole structure by the action of the diastase. 12. Circulation of Reserve Materials. After the reserve materials have been rendered soluble in the cell sap, and diffusible through the cell membranes, they move from the cells in which they are stored, by the processes of diffusion (see page 36), to the growing regions of the embryo, there to be used in part in the building up of new tissues, and in part to be consumed by combustion or respiration. It is 22 Introduction to Botany. this process of respiration which consumes oxygen and gives off carbon dioxide (see Experiment 37), and in so doing makes active the internal energy ^\ necessary to life and growth. In seeds having the reserve materials stored in the cotyledons, as in the Lima bean, the reserve materials need only to pass from these into the other parts of the embryo, leaving the cotyledons in a shrunken condition ; but in the case of such seeds as those of FIG. 4 . corn (Fig. 4) and castor bean, Median longitudinal section where the reserve materials lie through a grain of Indian corn. , . j r , , , r The median diagonal line de- outside of the embryo for the marks the endosperm or reserve greater part, at least, the cotyle- food of the upper half from the , 11- embryo occupying the lower dons act as absorbing organs, half of the grain. The fleshy an d enlarge as germination pro- cotyledon constituting the larger , , . , part of the embryo surrounds CCeds SO as to keep in close COn- the plumule and hypocotyi tact with the diminishing food above and below. Photomi- ** crograph x 3. supply. This is also well illus- trated in the seed of the date, where the cotyledon is like that of the corn in serving chiefly as an absorbing organ. In the seeds of the corn and date type the ferments lie partly within the cotyledon and partly within the cells which bear the food materials. As the reserve materials of the date seed, consisting chiefly of cellulose of bony hardness, become converted into sugar, they are absorbed by the coty- ledon, which then enlarges and occupies the space thus vacated (see Fig. 5). In this way the cotyledon keeps in close contact with the reserve materials and transports them from the seed as fast as they are rendered soluble ; Seeds and Seedlings. a fact of great importance, since the action of the ferments is hindered or entirely pre- vented if their products are allowed to accumulate within their field of action. A very notable example of the enlargement of the cotyledon while serving as an absorbing organ is seen in the cocoanut. Here the embryo is relatively small and lies embedded in the fleshy reserve food at the pointed end of the nut. As germination proceeds, a part of the cotyledon grows out through one of the three openings in the shell, and carries the plumule and hy- FIG. 5. pOCOtyl OUt with it, while Stages in the germination of a Date Seed : I, the young plant still attached to the the greater part of the coty- ledon remains within the seed, and as it absorbs the reserve materials it enlarges and fills the cavity (see Fig. 6). 13. Direction of Growth. The root of the seedling grows downward into the soil, and the shoot (stem and leaves) upward into the sun- light and air, and it matters not in what direction the seed may be lying in the soil. seed ; 2, cross section through a seed showing the small embryo to the left embedded in the hard cellulose endo- sperm ; 3, cross section of a seed in an early stage of germination ; 4, section through a seedling in an advanced stage of germination. The cotyledon remains in the seed and enlarges as the endo- sperm is absorbed. The stem or peti- ole of the cotyledon depending from the seed enlarges at its base and covers the plumule. The tapering end below the plumule is the hypocotyl. 5, a later stage showing the endosperm nearly ex- hausted and the cotyledon filling the cavity ; 6, surface view of a seed in an early stage of germination. After SACHS. The hypocotyl may be Introduction to Botany. pointing upward, but as the root grows forth it turns sharply downward, and the shoot as it develops, sharply upward. This is brought about by the in- fluence of gravity. In just what way gravity can exert such an influence is not known. We are accustomed to think of gravity as invariably at- tracting bodies toward the cen- ter of the earth, but on living and growing bodies it may exert an influence of quite another character. We might conclude, without an experiment, that gravity is the directive force ; for whether seeds are germinat- ing near the poles or at the equator, the roots always turn end view toward tfte center of the earth, of the " cocoanut " or stone of the and the shoots away from it. It fruit (corresponding to the stone i -, of a peach), showing the dividing 1S > however, a simple matter to lines of the three carpels which eliminate the directive influence compose the fruit. The embryo r . , , -, emerges through the lower open- f g ra Vlty, and by observing the ing. B, longitudinal section growth of seedlings under such through the fruit of the cocoanut, showing the embryo in process of circumstances to determine what germination ; e, the stone sur- effect gravity is producing under rounding the fleshy endosperm; ... _. / the enlarging cotyledon. The normal Conditions. Figures / plumule is growing upward anc j g illustrating the result of through the fibrous outer coat of the fruit. This coat is re- Experiment 41, page 15, show moved before the cocoanuts are how the i n fl uen ce of gravity may marketed. After WARMING. * be demonstrated by removing it from one set of seedlings while it is still operative on another set. rIG. o. Fruit of the Cocoanut : Seeds and Seedlings. If seeds are planted in a pan of sawdust which is kept revolving rapidly in a horizontal plane, centrifugal force may be made to overcome gravity, so that the roots grow away from the axis of rotation and the shoots toward it (see Fig. 9). FIG. 7. Seedlings of Indian corn grown in saw- dust in a Petri dish while revolving by clockworks one revolution per hour. The axis of revolution is hori- zontal, the plane of the dish vertical. Gravity as a directive agent is elimi- nated, and roots and shoots grow out in the direction in which they happen to be pointed. FIG. Seedlings of Indian corn grown in saw- dust in a Petri dish which was kept stationary in a vertical plane in the position shown in the figure. Gravity is acting as a directive agent, and the roots find and take the downward and the shoots the upward direction, irre- spective of the directions toward which they were originally pointing. Whatever part plants, as living beings, have taken in the selection of gravity to direct their growth, a wonderful discrimination has been exercised ; for, of the possibly available forces of nature, gravity is the only one which is practically constant in its strength, and in its direction of action, through all times of day and seasons, and in all positions over the earth's surface. The seedling can therefore depend with certainty on its root and shoot taking the right directions irrespective of the position in 26 Introduction to Botany. which the seed may be lying in the soil, or of the time or place of its germination. FIG. 9. Seedlings of Indian corn, beans, and peas grown in moist sawdust in a pan 17 inches in diameter, which was kept revolving at the rate of 185 revolutions per minute. The seeds were planted beneath the surface, and the seedlings have been uncovered for the photograph. 14. Roots the First to Grow. It has been noticed that the root first grows out and becomes established in close con- nection with the soil before the other parts of the embryo emerge above the surface. This insures that the seedling may not easily be dislodged from its position, and that the parts which are soon to be exposed to the drying influence of sun and winds may continually be supplied with water from the soil. If a seedling is removed with care from a sandy loam, the soil will be found adhering to the roots in large, loose masses, and when the soil is carefully washed away in water, it will be seen to have been bound together by means of numerous fine hairs growing from the roots. It Seeds and Seedlings. 27 will be found very difficult to remove all of the particles from these hairs, so intimate is their union. The signifi- cance of this close relation will be discussed in another chapter. 15. Completion of Germination. After the roots have become established in the soil, and the green leaves have unfolded to the sunlight, the young plant is in position to form its own food materials, and to be no longer depend- ent on food provided by the parent plant. The mother plant, however, often provides more than sufficient food to bring the offspring to a position of independence ; for, in many instances, the reserve food is not exhausted until long after the leaves and roots are ready to take up their office of providing new food supplies. The reserve mate- rials in the cotyledons of the oak, for example, do not become exhausted until the close of the second year's growth. The process of germination may be considered completed when the seedling is ready to provide for itself, for it would be manifestly incongruous to speak of the young oak at the beginning of the second year of its existence as still in the process of germination. 16. Size of Seeds. The size of the seed appears to have little or no relation to the size of the parent plant. The cocoanut and cottonwood trees are both large trees when fully grown, yet the cocoanut, as we find it on our market, weighs about 750 grams (including the shell or stone, which is not a part of the seed), while a cottonwood seed as it floats from the tree weighs about 0.0015 gram. What the size and rate of growth of the plant shall be depends upon potentialities transmitted to the seed from the parent plant that are quite beyond our powers of observation. CHAPTER III. ROOTS. OBSERVATIONS. 42. Nearly fill two wide-mouth bottles with a soil com- posed of one third black loam, one third rotted manure, and one third sifted sand. In one bottle, plant a soaked seed of Indian corn, and in the other a soaked seed of Lima bean, and incline the bottles at an angle of 45. Notice whether the roots take the same direction in both cases. If any of the roots reach the side of the bottle, note the behavior of their tips as they make their way between the soil particles. Study with a lens and note the relation of the root hairs to the soil particles. How close to the apex of the root, and how far back from the apex, do the root hairs grow ? 43. Soak seeds of barley in water over night, and plant between pieces of moist carpet paper, or blotting paper, about three inches square. Prepare seeds thus for each student. Keep in a covered dish in a warm place, and do not allow the paper to become dry. After the roots have grown out for an inch or more make drawings to show the root hairs. 44. Place a piece of polished marble at the bottom of a flower pot, or, instead of the marble, a clam or oyster shell with the concave side up. Nearly fill the pot with the soil mixture above described, and plant in it a few seeds of soaked Indian corn. After a few weeks, if the corn has 28 Roots. 29 made a good growth, remove the soil from the pot and note the effect of the roots on the surface of the marble or shell. Does this teach anything as to the possible effect of the roots on the limestone constituents of the soil ? 45. To demonstrate the force with which roots absorb water from the soil, cut a groove in the form of a circle about two centimeters in diameter, by means of the edge of a three-cornered file, at the large end of a hen's egg. Carefully remove the shell within the circle, guarding against puncturing the delicate skin. File with the flat face of the file at the small end of the egg until a thin area about four millimeters in diameter has been produced, make a small hole in the shell at the thin place, and blow out the contents by means of a glass tube drawn out in a flame to a fine point. In this "operation the tube must not entirely close the opening in the shell. Set the egg, large end down, in the mouth of a wide-mouth bottle which has been filled with water, and fill the egg with thin sirup colored with an aniline dye. A test tube drawn out in a flame to a fine tube is an excellent funnel for this purpose. Hold a piece of small glass tube, about one meter long, upright against the upper end of the egg and over the hole, and fasten it firmly in position, and water tight, by means of melted sealing wax. Keep the bottle filled with water, and watch the progress of the experiment. In ab- sorbing water from the bottle the artificial cell formed by the egg and sirup acts practically in the same manner as the root hairs in absorbing water from the soil. 46. Make a cross section of a root of corn or bean and treat with phloroglucin (see page 387). The elements which are colored red are the water-conducting elements into which the water passes from the root hairs. They are in reality long tubes, formed by the fusion of elongated 30 Introduction to Botany. cells, end to end, which extend continuously through the stem into the leaves, where they branch and help to form the veins and veinlets. Make similar sections of a root, not more than three millimeters in diameter, of some woody plant, and treat with phloroglucin as before. The ele- ments, which in this instance are colored red, consist of wood fibers in addition to the water-conducting tubes. The larger openings of the latter can easily be seen by means of a simple lens. 47. Make a cross section of a small sweet potato, which is in reality a root, and treat with the iodine solution. The section is stained purple, because it is filled with starch which supplies with food the young shoots that spring adventitiously from the root. Plant some sweet potatoes in moist sand and keep in a warm place. As the shoots develop, what change is noticed in the size of the root? 48. Make cross sections of dodder, which is parasitic on balsam, stinging nettle, or some other herbaceous plant. This material gives best results if it is taken in a young and tender condition and placed in 70 jfc alcohol for a time, and afterwards preserved in equal parts of alcohol, glycer- ine, and .water. Or it may be kept from the first in a 2 jfr formalin solution. Select a section showing the penetra- tion of the roots of the dodder into the host plant. Treat first with phloroglucin and then mount in chlor-zinc-iodide (see page 381), or mount in the latter reagent alone, and examine with the compound microscope. An examination with a simple lens even will give a fairly good idea of the intimate relation between the parasite and its host. 49. Take germinating seeds of Indian corn whose primary roots are about one centimeter long, and with waterproof India ink make marks on the roots one milli- meter apart, beginning at the apices. On other roots Roots. 31 make heavy, continuous lines running their full length. Place the seedlings in moist sawdust, and after a day notice whether the marks have separated at one portion more than at another, and whether the continuous mark has become broken at one portion more than at another. What do these experiments teach as to the regions of greatest elongation in roots? 50. Examine the roots of trumpet creeper, which are growing into some support. Do they appear to arise at a definite place on the stem ? Do they grow directly toward the support, or do they seem to have been uncertain as to the proper direction to take? How deep do the roots pen- etrate into the support ? If growing into a tree, do the roots seem to have penetrated to a sufficient depth to take sap from the tree ? The material for this study can be secured at any time during the year. It is a good plan, however, to gather it during the growing season and keep it in jars of 2 fy formalin. 51. Early in the spring, when the buds begin to swell, cut off a grape vine about six inches from the ground, and attach a long glass tube to the stump by means of a short piece of rubber tube. Tie the glass tube to a support so that it is held vertically. Keep note of the rapidity of the rise of sap in the tube. 52. Cut off a small branch of willow and place it in a bottle of water. Set the bottle in a warm place and keep the water replenished. Note from time to time whether roots are forming in or above the water, and if so whether they are formed in definite order. DISCUSSION. 17. Functions of Roots. The roots, of plants have to perform the functions of fixation, mechanical support, ab- Introduction to Botany. sorption and conduction of fluids, and storage. In follow- ing the development of the seedling, we have noticed that its first efforts are directed toward the formation of its root system. It would be hazardous for seedlings to develop parts above the ground before an anchorage has been made in the soil, for in that case the young plant could easily be torn or washed from its position by storms, and death would likely result from lack of water if the leaves were spread out above the ground before connection had been established with the water of the soil. 18. Growth of the Root As shown by Experiments 41 and 49, the root, elongat- ing only near the apex, is directed downward by grav- ity. The delicate root apex, of course, meets with obstruc- tions, but it is protected by a cushion of cells known as the root cap (see Fig. 10). Being in a state of growth, and longitudinal section of a Root Tip. it is quickly responsive to n, a root hair ; m, a young lateral root; j ts surroundings, and, turn- /, the root cap. Tracheal tubes are . j t_ i_ shown near the center in both cross and ing aside when it meets With longitudinal section. Particles of soil are obstructions, it paSSCS along represented clinging to the root hairs. A c the course of least resist- ance. While the root is thus threading its way among the soil particles, hairs are being formed on it, always a short distance back of the apex, keeping pace with it as it advances in growth and gradually dying off on the older portions. Thus the root hairs, which are the main absorb- FlG. 10. Diagrammatic representation of a cross Roots. 33 ing portions of the root, are continually brought into new parts of the soil, where fresh supplies of materials, suit- able for forming the food of the plant, are to be obtained. 19. Importance of Root Hairs. The root hairs are organs of much importance, since they greatly increase the anchor- ing strength of the root and furnish an increased surface for the absorp- tion of water and other substances from the soil. (See photomicro- graph of root and root hairs of bar- ley, Fig. 11.) It has been estimated that the hairs on corn roots, for in- stance, increase the absorbing sur- face about twelve times. When plants are transplanted during the growing season, after the leaves have been formed, they are quite certain to wilt, because the newer rootlets with their root hairs are broken off, even when the greatest care is exercised. The best time to transplant is, therefore, in the fall, after the leaves have dropped off, or in the spring, before the new growth begins. 20. The Nature of the Soil. The value of a wide dis- tribution of the roots in the soil lies in the fact that, aside from the benefits of anchorage, plants must take from the soil, w r ater and certain other substances without which they could not live. The soil is therefore a subject of great interest in connection with the study of plants. There are various kinds of soils, but it may be stated in general that ordinary tillable soil consists of particles of rocks in va- rious degrees of disintegration, intermixed with vegetable FIG. ii. Photomicrograph of a root of Barley, showing root hairs forming near the apex and dying away behind. X 3. 34 Introduction to Botany. and animal remains which, on account of the large percent- age of carbon contained in them, impart to the soil its dark color. The process of soil formation from the disintegration of rocks can be seen to advantage in any abandoned quarry. The newly uncovered rocks are hard throughout, but those which have lain for some time exposed to the weather become so soft at the surface that they may easily be scratched, or a considerable amount of material may be scraped from them by the finger nail. After longer expos- ure, and particularly after the water imbibed by them has been frozen, the rocks begin to crumblaninto pieces of vari- ous degrees of fineness. In whatever way rocks become broken down whether by the solvent effect of water, the expansive force of freez- ing water, or the beating of storms ; by abrasion when carried along by torrents, or when hurled to and fro by the surf, or when ground as in a mill by glaciers the ac- cumulated particles in time form a soil for the growth of plants. But long before the new soil is occupied by the higher plants it becomes the home of myriads of micro- scopic forms whose remains contribute to its richness and put it in a physical condition better adapted to the recep- tion of the larger and more exacting plants. 21. Soil a Reservoir for Water. The capacity of the soil to hold water is dependent on the fineness of its particles ; for the finer the particles, the greater the number of small capillary spaces and the larger the surface exposed for holding water by adhesion. To take a concrete example: A cubic foot of round soil particles having a diameter of one inch would expose a total surface of 37.7 square feet, while a cubic foot of such particles one one-thousandth of an inch in diameter would present an aggregate surface r Roots. \ 35 -y ( ' of 37,700 square, feet. The greater surface presented by the smaller particles is of further advantage in giving the water increased opportunity to dissolve out from them cer- tain substances necessary to the food of plants. 22. Action of Root Hairs. The root hairs place them- selves in close contact with the soil particles, and conform to their irregularities of surface so completely as to embed and hold them fast. This accounts for the difficulty of washing away the soil from the roots without breaking off the hairs. The close relation of the root hairs to the soil is of great importance, for long after the capillary spaces have been emptied of their water by evaporation, the soil particles still retain a film of water about them from which the root hairs are able to draw supplies for the plant, even when the soil ap- pears dry. A better comprehension of the absorptive action of the root hairs will be obtained after an exami- nation of their structure and the circumstances governing their ac- tion. They are really greatly elongated outer or epidermal cells of the roots (see Figs. 1 1 and 12). Their outer wall, a (Fig. 12, A and B\ is quite thin, and composed of cellulose, a substance readily permeable to water. Within the cell wall is the live part of the cell known as the protoplast (all of the granular part in A\ consisting of the outer lin- FlG. 12. A, diagrammatic representation of a Root Hair; B, a more highly magnified detail, a being the outer cellulose wall, b the plasma membrane, and c the cytoplasm, d is the nucleus suspended in the cytoplasm. 36 Introduction to Botany. ing membrane, b, called the plasma membrane, a specialized part of the cytoplasm ; the cytoplasm, c ; and the nucleus, d. Plasma membrane, cytoplasm, and nucleus are alive, while the cell sap, which occupies the remainder of the cell cavity (all of the clear space within A\ and the cell wall are not endowed with life. The plasma membrane is readily permeable to water, but not to all substances which the water may contain in solution. Its chief ser- vic,e consists, not so much in keeping certain substances from entering the plant, as in prohibiting the valuable cell sap and portions of the living body of the cell from passing out and becoming lost to the plant. Thus, while vast amounts of water with substances in solution pass into the plant through the root hairs, only very small quantities of materials, useful in rendering soluble those substances which the plant needs, are permitted to pass out by the same channels. 23. The Process of Absorption. The process of the passage into the root hairs of the substances dissolved in the water of the soil is known as diffusion. The initial force which causes this probably results from the energy of motion of the molecules and ions of the diffusing substance. Those molecules and ions which possess the greatest energy of motion, or whose size and shape best conform to the intermolecular spaces of the membrane, will traverse the membrane most rapidly. When the molecules and ions of a substance in solution are in equal concentration, that is, are in equal number per unit of vol- ume on both sides of the membrane, and their temperature is the same, the number of them passing the membrane in both directions per unit of time will be the same. This is a state of equilibrium which can only occur between the soil and the root hairs in the case of those substances which Roots. 37 are not being withdrawn from solution within the plant, or are not being used by the plant in the manufacture of new compounds. The more a substance is being employed or transformed by a plant, so that its concentration is continu- ally diminished, the more it will enter from without ; in this way the supply is adjusted to the demand. If, on the other hand, a substance which is able to pass the plasma membrane is not being transformed by the plant, it cannot continue to enter after the concentration of its molecules and ions within the plant is equal to that in the soil water; in this way useless materials are kept from accumulating. This is true of the substances in solu- tion, but the solvent, which in this case is water, passes most rapidly from the region of less to that of greater concentration (see Experiment 45). The passage of water through membranes from regions of lower to those of higher concentration is known as osmosis. The cell sap of the root hairs is of greater concentration than the soil water; and since this condition is maintained by evapo- ration from the leaves and other above-ground parts, and by the employment of some of the water in the manufac- ture of plant food, the water continues to enter the plant from the soil. If the water is abundant, it may enter the plant even faster than it is evaporated or used, in which case the plant cells become stretched and turgid. In this way rigidity is given to herbaceous stems and leaves. But when the water in the soil runs low, evaporation may be in excess of its movement into the plant, and wilting results. 24. Importance of Water. Water, which is taken by land plants almost exclusively from the soil, is the solvent and vehicle of transport for all substances which enter the plant, and for those compounds as well which are manu- factured within the plant ; it contributes its own substance Introduction to Botany. for the manufacture of plant food, and it further serves the plant in affording strength and rigidity to the tender herbaceous parts. 25. Elements Necessary to Plants. There are certain chemical elements necessary to the nutrition of plants, which must be taken from the soil particles ; these are calcium, mag- nesium, potassium, sul- phur, phosphorus, and iron. Nitrogen is taken in part from the com- pounds of nitrogen in the -soil, and in part in- directly from the free nitrogen of the atmos- phere by means of mi- croscopic organisms which reside chiefly in the root tubercles of leguminous plants (see Fig. 13). Were it not for the fact that these elements, for the most part, are in the form of compounds insoluble in water, they would soon be washed away by the percolating water after heavy rains. They are, however, slowly rendered soluble by acids excreted by the root hairs (see Experiment 44), by carbon dioxide dissolved in the soil water, and by the oxygen of the soil atmosphere. It must be remembered that there are no openings in the root hairs, and only sub- stances in solution in water can be absorbed by them. FIG. 13. D, root of a leguminous plant bearing Tuber- cles; E, a cell from a tubercle containing bacteria, highly magnified ; F, some of the bacteria more highly magnified; .G, a cell from a tubercle after the bacteria have, in part, evidently been absorbed by the plant. After FRANK. Roots. 39 26. Free Nitrogen made Available. Although about seventy-nine parts in one hundred of the atmosphere con- sist of free nitrogen, plants, with the exception of certain microscopic forms, are not able to use it for food until it has been combined with other elements to form some solu- ble compound, such as nitrates and ammonia. These are obtained largely from the decomposing remains of plants and animals. It has long been known that clover, when plowed under, leaves the soil much richer in nitrogen, and the reason for this is now well understood. There are bacteria residing in the tubercles of the clover roots (see Fig. 13), and they in some way combine the free nitrogen of the atmosphere with the other necessary food constituents provided by the clover plant, and use. the sub- stances thus formed as food. After a time the bacteria become disintegrated, and are apparently absorbed by the clover," which, in this roundabout way, obtains the nitrogen after it has Been combined with other substances to form proteids. Finally, the clover decays and yields its com- bined nitrogen to the soil. By this remarkable cooperation of two widely different kinds of plant life the free nitrogen of the atmosphere is made available to all kinds of plants. 27. Extent of Roots. The roots with their rootlets and root hairs form a dense plexus threading the soil in all direc- tions. Being buried in the soil, their great extent is not easily apprehended. It has been estimated that if all the roots and rootlets of a single corn plant grown under good field conditions were placed end to end they would cover* a linear mile. The roots of some plants extend to great depths, and these plants are thus able to obtain water and continue fresh and green after the surface soil has become dry and plants with shallow roots have withered away. The roots of alfalfa, for instance, sometimes penetrate the 4-O Introduction to Botany. soil to a depth of from ten to twenty feet, this habit mak- ing it valuable for hay and pasturage in regions of scanty rainfall. 28. Path of Absorbed Substances. The water aiid sub- stances in solution pass from the root hairs toward the center of the root, where they enter tubes (see Figs. 10 and 42) which conduct them through the stem into the leaves. The osmotic force in the root hairs is sufficient to lift the water in the stem to a considerable height (compare Ex- periment 51), but this force is not of itself sufficient to carry the water up rapidly enough to supply the evapora- tion from the leaves, nor high enough to reach the tops of tall trees. Figure 10 shows the relation between the root hairs and the water-conducting tubes (called tracheal tubes be- FIG. 14. cause of their resemblance in floating water plant. The appearance to tlie trachea or. slender roots, destitute of root hairs, grow down in the water. Slightly magnified. 29. Roots of Water Plants. The roots of water plants are much less extensive than those of land plants. In the case of such plants as Lemna and Spirodcla (see Fig. 14), which float upon the water, the roots are few, short, and unbranched, and destitute of hairs. Such plants do not need an elaborate root system, since water and food sub- stances dissolved in it are available without stint at all times. 30. Roots of Parasitic Plants. Some plants have de- veloped parasitic habits and attach themselves to other plants by means of their roots, having no direct connection with the soil, but depending upon their host plant for the water and other necessary food materials. If the parasite Roots. has no green leaves, as in the case of dodder (see Fig. 15), it must depend upon its host for all kinds of food mate- rials, for the starches, sugars, oils, and proteids manufac- tured by its host. It is, in other words, a complete parasite. But if, as in the case of the mistletoe, it has green leaves of its own, it is entirely dependent on its host for the water and dis- solved soil materials only, and is then but partly parasitic. 31. Roots of Air Plants. The aerial roots of some tropical orchids and of other aerial plants (see Fig. 16) do not be- come embedded in a sub- stratum, but grow free in the air, and they must, therefore, be able to absorb rapidly the water which falls or gathers on them from the rain or dew. To accomplish this the outer layers of the cells of the roots are empty and their walls are perforated by minute openings through which the water can be drawn by capil- larity. It may be that the water vapor of the atmosphere is condensed within these cells, but experiments on this subject have given contradictory results. 32. Prop Roots. The prop roots growing at the basal nodes of Indian corn, and the famous prop roots of the banyan tree, grow downward to or into the soil. Supported in this way, the banyan tree is able to spread its branches over an area so large as to give shelter to an entire .village. FIG. 15. A, Cuscuta Europaea, or Dodder, twining about and parasitic on a hop vine and bearing a cluster of small flowers. B, diagrammatic drawing of a cross section of a hop vine through the plane where the roots of the dodder enter it and penetrate to its vascular bundles. X fS. After K.ERNER. Introduction to Botany, FIG. 16. Aerophytes growing on the trunk and branches of a tree. Aerial roots seen pendent from the branch on the left. Drawn from data in Schimper's Pflanzengeographie . Roots. 43 33. Clinging Roots. The roots growing on the stems of the poison ivy and trumpet creeper (Fig. 17), for in- stance, do not serve an absorbing function, but are merely employed in holding the slender stems upright against a support. If these plants are growing near a tree or wall they find themselves shaded on one side, and their roots grow away from the side of greater illumination and toward the object which is shading them ; in this way they are quite certain to find a suit- able support. 34. The Various Directive Forces. Thus we see that roots have quite diverse functions to perform and that they show a marvelous capacity for employing various forces to direct them in their growth. If they are to grow into the soil, gravity is chosen as a guide ; if into the body of some host, as in the case of dodder, the stimulus of contact is selected ; if toward some object of support, either light or gravity is chosen, as is most practicable. Even to any given force the various parts of the root system may react differently; the main roots growing in the soil are directed more or less downward ; the lateral roots spring- ing from these make greater or less angles with the line of gravity; while the ultimate branches may grow in any direction, apparently without respect to gravity. In this way all parts of the soil within the range of the roots are fully occupied, which would not be the case if the entire root system were impelled by gravity in one direction. The water in the soil, also, has a directive influence on the FIG. 17. Portion of a stem of the Trumpet Creeper, show- ing its clinging roots. 44 Introduction to Botany. growth of the roots ; if the water is distributed evenly, the roots develop evenly on all sides, but if the conditions are otherwise the roots tend to follow the direction of the greater water supply. 35. Adventitious Roots. We have noticed in the growth of seedlings that the first rootlets spring from the primary root at definite angles of di- vergence, but that on the stems of ivy and Cuscuta their places of origin are indefinite, in other words, these roots seem to arise adventitiously. When willow stems are cut off and placed in water, roots are formed in the same manner not far above the cut surface. Showing the method of Layering. A Xhe ability of plants to form branch is bent and pegged down , and covered with soil. After adven- adventitious TOOtS IS employed titious roots have formed on the fry horticulturists and florists branch it is severed from its parent stock. After BARRY. in the propagation of many kinds of plants by the pro- cesses known as layering and cuttage. In this way may be propagated currants, gooseberries, raspberries, grapes, roses, azaleas, fuchsias, etc. (See Fig. 18.) 36. Roots Defined. Although roots are called upon to perform various functions, and may be modified in form accordingly, they still have certain characteristics which distinguish them from other plant members. They are members of the plant body of indefinite elongation, pro- tected by a root-cap ; and they never directly bear leaves, although capable of producing adventitious buds. FlG - l8 - CHAPTER IV. BUDS AND STEMS. PROVIDING MATERIALS. Most of the material required in the study of buds and stems can be procured out of doors at any time before growth begins in the spring. If the study is to be taken up later in the season, twigs of horse chest- nut, cottonwood, and lilac with winter buds should be secured and kept in 2% formalin until needed. In those schools where the study of botany is begun immediately after the Christmas vacation, strong shoots of the above plants should be cut off and placed in jars of water at the beginning of the term, and kept in a warm place, in order that their buds may be unfolded by the time the study of buds in their win- ter condition has been completed. The twigs may be crowded into the jars quite closely, and there should be several twigs of each kind for every student. The water in the jars should be frequently changed. If Aristolochia is not at hand, it can be obtained of dealers in botani- cal supplies. 1 Branches of Tilia (linden) can be used to good advan- tage for sectioning if Aristolochia cannot be obtained, and branches of elm might be used, although less advantageously. Aristolochia, how- ever, is the best for this study. These branches and small stems of Indian corn should be taken during the growing season and placed for a week or so in 70% alcohol, and then kept in equal parts of alcohol, glycerine, and water until needed. This method of treatment makes it easier to cut good sections. OBSERVATIONS. 53. Make drawings of a twig of horse chestnut in its winter condition, showing the relative size and position of all exterior structures. Where did last year's leaves grow on the twig ? 1 Cambridge Botanical Supply Co., Cambridge, Mass. 45 46 Introduction to Botany. 54. Make drawings, on a larger scale, of a terminal bud, a lateral bud, and any structures related to them. What is the relation as to position between the leaves and buds of the twig ? 55. Select one of the largest buds, and pick off the bud scales carefully, so as not to injure them. Arrange them in separate groups in the order in which they were removed, each group being composed of the scales which encircle the stem once in the successive spirals, or whorls. Draw a typical scale from each of the groups. When the scales are all removed, draw the inner structures which were pro- tected by them (scale, x 5); first, as they stand in their natural position on the stem, and second, when removed and laid out for examination separately. If the parts are folded together make a drawing to show the manner of folding, and then spread one of them out and draw in the expanded position. Use the lens for this work, and draw in the details which can be seen with it. 56. Make cross sections of a bud, beginning near the apex and sectioning in successively lower planes until the parts protected by the scales are seen to best advantage, and then clraw to the scale x 2.5. Identify the different parts of the sections by the aid of the dissections already made. 57. Pay particular attention to the protection afforded the tender inner parts of the bud by means of the scales or other structures or devices. The inner parts need protection 'against drying, sudden freezing and thawing, attacks of parasites of various kinds, and mechanical in- juries due to the beating of storms and abrasion from other causes. In what ways are these different sources of danger guarded against ? 58. Make a median longitudinal section through one of Buds and Stems. 47 the largest buds, and draw the cut surface. The drawing should show the outline of all the parts with perfect clear- ness. Do not make any lines which have no distinct significance. 59. What portion of this twig was formed last year? What portion was formed the year before ? Is there any portion of the coming season's shoot present in this twig ? Label the drawing of the twig according to the different years' growth, and determine by cross sections whether there is any relation between the internal structure and the age of the parts of the twig. 60. Make drawings of buds in different stages of unfold- ing so that the following questions may be answered by reference to the drawings : What changes do the bud scales undergo ? What finally becomes of the bud scales ? Do the bud scales in any way leave their impress upon the twig? What changes do the inner parts of the bud undergo ? Do the parts increase in size ? in number ? Do they change materially in form ? Are their relative posi- tions changed ? Are any new parts produced, or does the unfolding of the bud consist simply in changes in parts already present ? 6 1. Turn back to twigs in winter condition and deter- mine the location of the bud scales of last year, and of the year before that, etc., and see that your drawing takes proper account of them. 62. Count the leaf scars belonging to the different years' growth to determine whether the number of leaves produced each year is the same. 63. Determine the number of vertical rows of leaf scars, and the angular divergence of the leaves on various twigs, selecting those which have made a vigorous growth and are straight and untwisted. A good way to determine 48 introduction to Botany. the number of vertical rows is to stick pins or dissecting needles into each leaf scar perpendicular to the tangent at that point, passing spirally up the stem, omitting none of the scars, until the scar is reached which stands immedi- ately above the initial scar, that is, the one with which the start was made. When the twig is now held in front of the observer, parallel to the line of vision, the number of vertical rows of leaf scars may easily be counted and the angular divergence of the rows determined. The angular divergence of a leaf from the one next above or below it is now to be determined. Suppose that in counting the scars it is found that in passing once around the stem the fifth scar is immediately above the initial scar; then it is plain that the angular divergence of the leaves from each other is one fifth of 360, or 72. But suppose the five leaves are distributed over two turns of the stem ; then it is evident that they are twice as far apart as in the first case, that is, their angular divergence is now twice 72, or 144. If examples of this sort were multiplied, it would be seen that the angular divergence of the leaves would be that fraction of 360 whose numerator is the number of times the circumference of the stem is passed over, and whose denominator is the number of intervals traversed in passing spirally from the initial scar to the one directly above it. Of what use is a definite angular divergence of the leaves ? 64. Study in like manner cottonwood and lilac. 65. Make thin cross sections of a one-year-old stem of Aristolochia, and treat with phloroglucin and chlor-zinc- iodide, or double stain with cyanin and erythrosin (see page 384). Examine with a simple lens or with the low power of the compound microscope. ^ On the outside is the epidermis, a (Fig. 19). Within this is a zone of tissues Buds and Stems. 49 known as the primary cortex, extending to and including the row of cells, b, which is termed the starcJi sheath or endodermis. The groups of tissues within the endodermis make up the central cylinder or stele. The groups of tis- sues, d, which are disposed in the form of an interrupted concentric zone, are known as the vascular bundles. The tissues between the en- dodermis and the vas- cular bundles constitute the pericycle, c. The tissue surrounded by the vascular bundles is termed the pith, e. The tissue connecting the pith with the pericycle, and accordingly run- ning radially between the vascular bundles, is termed the medullary rays, f. Cross section of a one-year-old stem of Aristolo- Aristolochia which are chia. a, epidermis; b, endodermis; c, peri- treated with nhloroHu c>cle; d> vascular bundle : ', P ith = ff> cam - r S m bium ; A. sclerenchyma ring of the pericycle; Cin and chlor-zillC- , collenchyma ; / medullary ray. iodide, it is seen that the vascular bundles consist of two distinct parts an inner part which is colored red by the phloroglucin, and possesses relatively large openings, and an outer part which is col- ored purple by the chlor-zinc-iodide, and whose cells are relatively small. The inner part, which is known as the xylem, is the water-conducting part of the bundle; while the outer part, termed the pJtloem, is the food-conducting part. The small, brick-shaped, thin-walled cells, g, be- FiG. 19. 50 Introduction to Botany. tween the phloem and xylem are the cambium cells, which, during the growing season, rapidly divide and form new cells that finally become altered into the tubes, etc., of the xylem and phloem. As the stems grow older, cambium is formed between the bundles, and thus is produced a complete ring of delicate cells which permits the bark to be separated readily from the wood. The bark is composed of all the tissues outside the cam- bium ring, so that when the bark is stripped off the phloem portion of the vascular bundles goes with it (see Fig. 21). Turning again to the section of Aristolochia, one sees that a portion of the pericycle (//, known as the sclerenchyma ring) is composed of cells which are thick- walled and lignified, as indicated by their being stained red by phloroglucin, or blue by the cyanin. A longitudinal section would show that these cells are elongated in the direction of the long axis of the stem and are closely bound together, being thus well adapted to give strength to the stem. If the section is carefully studied, it will be seen that these different tissues are not separated from each other by lines, such as the beginner might be tempted to use in drawing them, but that they owe their demarca- tion to the fact that the cells composing them differ in form and size, in the character of their contents, and in the thickness and kind of their walls. The tissues are adapted to perform various functions by their different characters and relative positions. The epidermis has an outer wall which is infiltrated with waxy substances and is thus adapted to prevent the inner tissues. from drying up ; the epidermis has, therefore, a protective function. The thick-walled cells of the outer part of the primary cortex (z, known as the collenchyma) are chiefly for giving strength. The inner cells of the primary cortex Buds and Stems. 51 are thin-walled, and the walls are made of cellulose, a sub- stance which is easily permeable to water and substances in solution. These cells are therefore fitted for the storage and slow conduction of materials ; and since they lie near the periphery and are accessible to light, they contain the same kind of green chloroplasts which reside in the leaves, and use the energy of the light in manufacturing food materials (see page 87). The outer portion of the peri- cycle, on account of the thickness and lignification of its cell walls and of the elongation and close union of its cells, is adapted to give strength and rigidity to the stem. The inner portion of the pericycle, having thin, cellulose walls, is adapted to the storage and slow conduction of materials in solution. The phloem portion of the vascular bundles probably carries proteid and other food materials rapidly up and down the stem as needed, being fitted for this purpose by its long, thin-walled, tubular cells, which are separated longitudinally by partitions having perfora- tions, through which materials may readily pass. The xylem portion of the bundles carries water upward from the roots through its tracheal tubes, while the wood fibers associated with the tracheal tubes contribute to the strength and hardness of the stem. When we consider the vascular bundle as a whole we see that its conductive function is preeminent. The medullary rays carry materials radially to and from the bark and pith and to and from the vas- cular bundles. The pith may, in its young state, conduct materials up and down as needed, but as it gets older it dies and contains air only, or it may break down entirely. Study also cross sections of an Aristolochia stem which is several years old and note the changes which have taken place in the different tissues since the first year. 66. Make a diagrammatic drawing of the different zones Introduction to Botany. of tissues seen in the cross section of the stem, simply out- lining them in right position and proportion, and with the colored pencils give each part having a distinct function a color of its own. For instance, color the epidermis blue, the thick-walled cells of the primary cortex red, and its thin-walled cells green, the strengthening ring of the peri- cycle red, the inner portion of the pericycle, medullary rays, and pith yellow, the phloem purple, the xylem orange, and leave the cam- bium uncolored. Run dotted lines from the different parts and at the end of each line write the name and function of the part. 67. Make sections of the stem of Indian corn where it is about one centimeter in diameter, and treat as di- rected for Aristolochia. Here the bundles are scattered promiscuously throughout the stem, and there is no distinction into pith and medul- lary rays (Fig. 20). The stem is given strength by the thick-walled cells of the primary cortex lying at the periph- ery, and by a sheath of somewhat similar cells around each bundle. The vascular bundles consist of the same parts as those of Aristolochia, the xylem facing the center and the phloem the circumference. There is, however, no cambium between the two parts of the bundle, and the latter does not therefore increase indefinitely in size, but soon attains to its maximum dimensions. In corn, the FIG. 20. Cross section of a stem of Indian corn, a, epidermis; b, primary cortex; c, peri- cycle; d. vascular bundle; e, ground tissue. Buds and Stems. 53 general ground tissue in which the bundles are embedded serves the functions of the pith, medullary rays, and thin- walled portion of the pericycle and primary cortex, as stated for Aristolochia. 68. Make an outline drawing of the parts of the cross section of the stem of corn and use the colors to designate the same functions which they were made to represent for Aristolochia. Thus the epidermis would be blue as be- fore, the thin-walled cells of the primary cortex green, while its thick-walled cells would be red ; the thin-walled tissues in which the bundles are embedded yellow, the phloem purple, the xylem orange, and the narrow zone of thick-walled tissue bordering the bundles red. The colors will assist in comparing the different parts of the stem from the standpoint of their use, blue meaning that pro- tection is given ; green, that food is manufactured, tempo- rarily stored, and slowly conducted away as needed ; red, that strength is imparted ; yellow, that food is stored and slowly conducted ; purple, that food materials, and partic- ularly proteids, are rapidly carried either up or down the stem where need is urgent; orange, that water is rapidly carried from roots to leaves ; uncolored, that the cells are rapidly multiplying and increasing the diameter of the stem. 69. Plant seeds of garden balsam in moist sawdust, and keep watered with well water. As soon as the seedlings appear place one lot near a window, and another lot on a side of the room remote from the windows where the light is not intense. Note the difference in rate of growth, in the relative lengths of the internodes, and in the size of the leaves. Do the stems grow upright ; if not, what force is interfering with gravity? Carefully remove some of both lots of seedlings from the sawdust and place in a 54 Introduction to Botany. tumbler or wide-mouth bottle containing a weak solution of fuchsin, and keep the roots covered with this solution until a red color appears in the veins of the leaves. The stain will color the tissues through which it passes and thus mark out the paths of the ascent of water. Balsam stems are sufficiently transparent to allow the tissues near the center to be seen from the outside. 70. Remove a ring of bark about an inch long from some twig or sapling which is in leaf (the willow serves excellently for this and the following experiment because its bark is strong and easily separates from the wood), and note whether the leaves wither. Watch the experiment for several days. Operate on another twig or sapling in the following manner : Make a longitudinal incision through the bark an inch or more long, depending on the diameter of the stem, and then, with a thin, smooth stick work the bark loose around the stem, inserting the stick through the longitudinal slit. Cut the wood of the stem nearly in two, and then bend the stem until it breaks, the broken ends protruding through the slit in the bark. Trim off the ends so that they will not touch each other ; then hold the stem upright so that the ends are again cov- ered by the bark, and bind splints around the outside to keep them in place. Care should be taken during this operation that the bark is not injured except by the longi- tudinal slit. Note the effect on the leaves in the course of a few hours. What do these experiments teach as to the region of water ascent in plants ? 71. Remove a ring of bark from a branch or sapling that can be conveniently watched, and note the result at the end of the season's growth. What do the results teach as to the region of transfer of food materials necessary to the building up of new tissues ? Buds and Stems. 55 72. Make thin cross sections of stems of elm, cotton- wood, or other woody plants which were placed in alcohol in late summer, and treat with iodine. Can reserve food in the form of starch or proteids be made out? (The starch would be colored blue by the iodine, and the pro- teids from yellow to brown.) Compare with these sec- tions others of stems of the same plants taken at the time of unfolding of the buds in the spring. What changes have taken place in the reserve materials ? DISCUSSION. 37. Upward Growth of the Shoot. We have noticed that in the germination of seeds the shoot grows straight upward into the sunlight and air just as uniformly and persistently as the roots grow downward into the soil, and it might be inferred from this alone that the upward growth of the shoot is just as necessary to the well-being of the plant as the downward growth of the root. It has been noticed that as the shoot reaches the surface, either the cotyledons spread out in the form of thin green leaves, or the first leaves of the plumule bud quickly unfold and place their broad surfaces more or less at right angles to the light from the sky, as in the case of the Lima bean, whose cotyledons are so gorged with food materials that they are prevented from developing into useful foliage leaf forms. As the stem continues in its elongation, it puts forth new leaves until it is nearly concealed by them and is apparently subordinate to them. It may, in fact, be stated that the chief function of stems is to bear leaves, in such positions and at such distances apart as to give them free access to the sunlight and air, and to keep them in communication with the water and other raw food ma- terials which are absorbed by the roots. 56 Introduction to Botany. 38. Protection against Drying. As soon as the shoot appears above the ground it is in danger of drying up, or of becoming bruised or broken. To guard against drying, the outer wall of the epidermis or exterior layer of cells becomes infiltrated with a compound of fatty and waxy substances known as cutin, and so is rendered almost im- pervious to water. Every one has noticed how quickly an apple shrinks and drys when its epidermis has been removed by paring, and it would be a simple matter to demonstrate that any young or succulent stem would quickly become dry if its epidermis were stripped off. 39. How Stems are Strengthened. In order to strengthen the stem, the walls of the cells in certain regions become thickened, and sometimes woody, and the cells often be- come elongated and more or less interlaced, as in the case of wood and bast fibers. As evidence of the effectiveness of wood and bast in strengthening stems, let the great elas- ticity and strength of some of the well-known woods, such as hickory, be called to mind, and the fact that hemp rope and linen thread are made from the bast of plants. The stress which the strengthening elements must over- come is produced usually by the wind and the weight of the crown of the plant. The force of the wind bends the stem, producing a stretching of the elements on one side and a compression on the other, while the weight of the crown produces a compressing effect simply. It is clear that if a given amount of strengthening material be distributed in the form of a hollow cylinder, all stresses of the above nature can be overcome to the best advantage. We find, accordingly, the strengthening elements of the pericycle of Aristolochia arranged in this form, and the same is true of the strengthening elements in the primary cortex of corn, and of the wood and bast fibers in the Buds and Stems. 57 stems of plants in general ; but in the roots, where the stress is applied more nearly as a straight pull, we find the strengthening elements in the form of a compact column at the center, a form which is best adapted to resist a longitudinal pulling stress. In the distribution of their strengthening elements, plants have been obliged to take account of many things, such as economy of materials, the free circulation of materials, and the formation of branches. 40. Conduction of Materials. The conducting elements of the stem are quite as important as the strengthening elements. The leaves give off large amounts of water by transpiration, and must, therefore, constantly receive com- pensating supplies from the roots. "To facilitate the pas- sage of water, long tubes are provided, extending from the roots into the leaves. These tubes, known as tracheal tubes, have relatively large openings, and their walls are thickened in various ways (see Fig. 21) so as to strengthen them, and at the same time leave thin places for the pas- sage of water into the tissues along their route, and to allow the passage of food materials into the tubes while they are yet in state of formation. The thin places in the tubes also serve another purpose every spring, in permit- ting the reserve food materials in the underground parts and lower regions of the stems to pass into the tubes and be carried rapidly upward to the unfolding buds by the ascending currents of water. The tracheal tubes have cross partition walls in them which are about eighteen inches to three feet apart ; these are thin, however, and do not much retard the passage of the water. The tracheal tubes lie in the xylem portion of the vas- cular bundles and are thus within the cambium ring. Accordingly when the bark is removed from a stem, the 58 Introduction to Botany. tracheal tubes are left intact, since the bark separates at the cambium ring (see Fig. 21). This accounts for the fact that the leaves do not wither when the bark is removed by girdling. While water is being supplied through the roots the most important process of the manufacture of food mate- Diagrammatic representation of the structure of a Stem, the bark being partly stripped off at the cambium ring. z o and p, tracheal tubes, which carry the water upward from the roots ; thin places are seen in the walls of these tubes in the form of pits and rings, w and x, sieve tubes which carry food down from the leaves, or up, as needed, v, medullary ray, which carries water and food radially to and from the bark and the wood as needed, z, bast fibers. Cells of the cambium ring are clearly shown to the right of the sieve tube, x. rials is taking place in the leaves, and highways must be provided for the transport of these food materials down- ward and upward wherever growth in length or in thick- ness is taking place. The tracheal tubes could not answer this purpose because the upward movement of the water through them would prevent the passage of food materials Buds and Stems. 59 downward. The sieve tubes in the phloem portion of the bundle outside the cambium ring (see Fig. 21) seem to be .the highways for these food materials. The sieve tubes are 'thin-walled and allow the food materials to pass to and from the surrounding tissues as needed. They have cross partitions at frequent intervals to strengthen them, but the partitions are perforated so that materials may pass rapidly through them. 41. Effect of Girdling. When a tree is girdled, the sieve tubes are removed with the bark (see Fig. 21), and the parts of the stem and of the roots below the girdle are no longer supplied with food. While the portions of the stem above the girdle increase in thickness and length as usual, all parts of the plant below the girdle are restricted in growth because the main food supply is shut off. If the bark of a stem is removed early in the spring, before the leaves are out, the usual process of the unfolding of leaf and flower buds may still take place because the reserve materials stored in the underground parts and in the lower portion of the trunk may be carried upward by the water currents in the tracheal tubes ; but the following year, if the bark has been completely removed in the girdle, and no twigs, bear- ing leaves have been allowed to grow below the girdle, the roots will not have stored in them the food necessary to the production of new rootlets and root hairs, and thus can no longer absorb the water necessary to the resump- tion of growth. The advantage of girdling trees which are to be cut, down lies in the fact that the stump and roots below tHe girdle will thereby be prevented from re- ceiving the food which might be employed in the produc- tion of new shoots from adventitious buds on the stump or roots. In stems of the type of Indian corn and palm there can be no separation of the food-conducting and the water- 6o Introduction to Botany. conducting elements by the process of girdling, for the reason that the bundles are scattered promiscuously throughout the stem (Fig. 20). 42. Summary of Structure and Function. When we re- view the details in the plan of construction of typical stems, we see that they are so admirably adapted to give strength and facilitate transport that trees can withstand the storms of centuries, and the inter- change of materials between roots and leaves can continue without interruption even in trees which have reached a height of four hundred feet. We see that the strengthening elements are laid down ac- cording to approved mechan- ical principles, and that the conducting system is a double Diagram showing medullary rays from . J cross, tangential, and radial points of highway along which mate- n PP site directions without hindering each other in the least degree. We find that the movement of materials radially is provided for by the medullary rays, which extend individually only a short distance longitu- dinally, and so are prevented from transporting materials in any other than the radial direction (see Fig. 22). 43. Transporting Forces. The forces which are con- cerned in carrying the water upward have not yet been demonstrated with certainty. Atmospheric pressure does not suffice to carry water to the height of tall trees ; capil- larity in the tracheal tubes cannot lift the water beyond the height of a middle-sized tree ; and osmotic pressure in Buds and Stems. 61 the roots cannot provide water fast enough to supply the loss by transpiration. Neither does the lifting power appear to be due to living cells in the roots or stem acting after the manner of a heart, or in any other way ; for after these cells have been killed by poisonous solutions the water continues to rise and evaporate from the leaves. It seems probable that the leaves themselves assist in lifting the water, perhaps by osmotic action between the tracheal tubes and the parenchyma cells in the leaves; but this has not been satisfactorily demonstrated. The problem of the ascent of water, although apparently simple on the face of it, has been one of the most elusive in plant physi- ology. The forces concerned in the rapid movement of food materials through the sieve tubes also remain undem- onstrated. Diffusion would account for slow movements, but the sieve tubes are evidently designed for conducting more rapid hydrostatic currents. ^ 44. Direction of Growth. We have seen that the shoot of the young seedling employs gravity to direct its course upward. After it appears above the ground, however, it does not necessarily continue in a vertical direction, but may grow more or less nearly horizontal, and may even turn downward. If the stem becomes more intensely illuminated on one side than another, it usually grows toward the region of greatest illumination, but in some climbing plants it may grow in the opposite direction and thus keep in close contact with its support. 45. Gravity as Guide. While the plant employs grav- ity as a guide in bringing the shoot out of the ground, it also uses the same force in conjunction with light to guide it in placing its branches at various angles to the vertical, as its needs may require. Although it may be stated as a rule that shoots which are formed beneath the surface of 62 Introduction to Botany. the soil are directed upward by gravity, this is by no means always the case. Certain underground shoots of the po- tato, for instance, are directed downward at various angles, and the underground shoots of the goldenrod are guided in a horizontal direction. In Sagit- taria variabilis we find an in- teresting example of somewhat diverse habits. Radiating in various directions from the parent plant (m, Fig. 23) are hor- izontal underground shoots (g) t which finally turn upward at the apices (//) and produce leaves above the surface. Roots are produced at the basal node of the upright shoots, which then become independent indi- viduals (z). Later in the season, under- ground shoots (/) are produced which grow vertically downward for about a foot, and then turn upward at their apices for a short distance and form bulbs (e) that become filled .with Sagittaria variabilis. d, last year's tuber, from which the central plant (m) has sprung; g, off- shoots from m\ h, terminal bud of g, which has turned upward and will produce a plant like i ; f, offshoot which has grown down into the mud and will produce a tuber similar to e, which is a tuber of the current season destined to survive the winter and then produce a new plant, as d has done. Buds and Stems. 63 reserve food materials, and in this position survive the winter. In the spring the terminal shoot produced from a bulb grows vertically upward (d) and sends forth leaves and flowers ; while at a node a short distance below the sur- face of the mud, roots are formed, and also buds, from which the horizontal shoots arise, thus bringing us back to the stage at which we began the cycle. This example is an exceedingly instructive one in showing how plants may employ any force acting in a definite direction (in this case gravity), not in impelling all of its parts in one direction, but as a fixed line from which may be determined the various directions toward which its different members should grow. It is also instructive in another way : it shows that plants are not inert bodies, but are possessed of a high degree of sensibility which enables them, in a certain sense, to perceive their condition and the forces within whose range they are lying. Notice, for instance, that the horizontal shoots of Sagittaria do not grow indefi- nitely in the horizontal direction, but after a suitable dis- tance from the parent plant has been traversed so that danger of crowding is avoided, they turn upward and pro- duce leaves and roots. So, too, the downward-growing shoot, having reached a depth where the winter may be passed in safety, turns upward and produces the bulb to which is intrusted, as well as to the seeds, the life of suc- ceeding generations. 46. Light as Guide. Where gravity cannot be employed as a guide in achieving certain results, light may be used instead. If the stem has a climbing habit and is supported by lateral outgrowths in the form of suckers or roots which are able to obtain foothold on walls, trees, etc., the shoot employs the line of propagation of the greatest incident FIG. 24. Mature plant and two seedlings of the Trumpet Creeper. The seedlings are growing toward the wall and away from the source of greatest illumination. On the mature plant the flowering branches are growing away from the wall and toward the source of greatest illumination. Buds and Stems. 65 light to guide it toward its support. The common trumpet creeper, Tecoma radicans, acts in this way. Figure 24 is a drawing from nature showing seedlings which have started at some distance from the wall toward which they have sharply turned ; their leaves, however, are facing the light. As this plant climbs a wall its shoots lie close against it, so that the clinging roots easily get a foothold. But the shoots that are to produce flowers as well as leaves FIG. 25. Ltnaria cymballaria clambering over rocks. After KERNER. turn toward the light instead of from it (see Fig. 24), so that the flowers may be easily detected by the insects and humming birds which assist in their cross pollination (see page 170). A no less marvelous example in which the sensibility of the plant involves a perception of its own condition (conscious recognition is of course not meant) is furnished by the behavior of the flower stems of Linaria cymballaria, a clambering plant which fastens itself to walls, etc., by means of suckers. The pedicels bearing newly opened flowers turn outward toward the source of greatest light so that the flowers are noticeable to those 66 Introduction to Botany. insects which are necessary to their cross pollination ; but after fertilization has been achieved and the production of seeds thereby insured, the pedicels turn from the light and deposit the seed pods in the crannies of the rocks, where they may find a suitable place for their germination (Fig. 25). 47. Formation of Leaves. We have noticed, in follow- ing the development of seedlings, that leaves are produced at definite intervals along the stem as the shoot elon- gates. The segments of the stem which bear the leaves are called the nodes, while the, portions of the stem be- tween the nodes are termed the internodes. An exami- nation of the apical bud of the shoot, with the simple lens, reveals the fact that the leaves are begun as lat- eral outgrowths of the stem quite close to the growing point, the apical bud consist- ing, in fact, of a succession Honey locust with deliquescent trunk. of immature, nodes, inter- nodes, and leaves. 48. Summer and Winter Buds. In some plants, the growing point of the shoot continues to give rise to new nodes, internodes, and leaves throughout the growing sea- son, so that when winter sets in there is a certain unripe portion of the shoot extending back from the apex which is killed by the cold, or its buds are weak, and the continu- ation of growth the following season devolves on buds on older portions of the stem. In such plants the crown is much branched and has no main central trunk (see Fig. 26). FIG. 26. Buds and Stems. 6 7 In other plants, such as the horse-chestnut, hickory, and cottonwood, the elongation of the stem ceases before the close of the growing season. In such cases a few of the last-formed internodes fail to elongate, while the leaves of some of the lower nodes subtending the short internodes grow up in the form of scales, completely enwrapping all of the parts above them, and protecting them against mechanical injury and the vicissitudes of weather. Such buds are quite certain to survive the winter, and, if stronger than the lateral buds, to continue the growth of the shoot the following spring, so that the main shoot of such plants is apt to retain its identity in the form of a central shaft ex- tending through the crown (see Fig. 27). Buds which ripen and prepare for winter are termed winter buds ; while the buds which do not ripen, and die or re- main weak in consequence, may be called summer buds. 49. Protection afforded Winter Buds. The study of the winter buds of the horse-chestnut and cottonwood has shown that the leaves formed at the uppermost nodes are ordinary foliage leaves in an embryonic state, and conse- quently in need of protection. The amount and character of protection afforded to the tender parts of winter buds is quite different for different plants. As has already been observed by the student, the outer scales of the buds of FIG. 27. Oak with excurrent trunk. 68 Introduction to Botany. horse-chestnut 'and of hickory are hard and dry and well adapted to give protection against mechanical injury, while the hairs growing over the scales tend to keep them separated slightly, and so form dead air spaces which retard the escape of water from the succulent parts of the bud, and, on account of the slight conductivity of air for heat, protect the inner parts against sudden changes in tempera- ture. In the winter buds of the cottonwood, the tender parts are prevented from drying up by resinous substances which hold the scales closely together. The amount of protection required by buds varies greatly for different plants, and depends largely upon the ability of their pro- toplasts to withstand adverse conditions. The buds of some plants are able to pass through severe winters in safety without any special means of protection. Even in the arctic regions there are plants whose buds are able to survive the intense cold while in a succulent, half -formed condition. The degree of protection given to buds seems, therefore, to be regulated by the needs of the living cells. 50. Disposition of Leaves in Buds. The manner in which the embryonic foliage leaves are packed away in the bud is not the same in all cases ; but, however these details may vary, the leaves already possess in the bud the regular angular divergence on the stem which is found in mature shoots, and this facilitates their disposition in the very small compass of the bud. 51. Unfolding of Winter Buds. The unfolding of winter buds in the spring is essentially the resumption of growth in parts already formed. The short internodes and the minute leaves quickly elongate and expand, and almost in a day the trees are again covered with foliage. Such remarkable development would be impossible if reserve food materials were not already at 'hand for the building Buds and Stems. . 69 up of new tissues. The reserve materials can be demon- strated by using tests for starch, proteids, sugar, oils, etc., chiefly in the medullary rays and wood parenchyma cells of the stems and underground parts. Before these mate- rials are needed in the spring, those which are insoluble or poorly diffusible are changed by appropriate ferments so that they can pass by diffusion from cell to cell, or be carried more rapidly upward by the ascending currents of water. Buds which remain attached to the parent plant and are able to draw upon it for their food do not need to have the reserve materials stored within their own tissues, as in the case of seeds which are cast off from the parent and left thereafter to shift for themselves. 52. Leaf and Flower Buds. Dissection of the terminal buds of the horse-chestnut reveals the fact that many of them contain flowers as well as leaves, while the terminal buds of the lilac may contain only flowers. In the cottonwood we find many of the lateral buds containing flowers only, while the terminal buds contain only leaves. When we inquire the reason why the growing point of certain form- ing buds gives rise to leaves and that of others to flowers, or to both leaves and flowers, we are unable to obtain a satisfactory answer. We know, however, that some peren- nial plants produce only leaf buds for a number of years, and are not able to form flowers until they have attained a certain age ; we do not expect apple trees, for instance, to bear flowers until they are five years old or more. The century plant does not produce flowers until it has attained an age of twenty to thirty years. We know, too, that shoots which would otherwise terminate with winter budk containing leaves only can be made to terminate with buds containing flowers if the branch on which the shoot is borne is pruned back, or if the roots are pruned. By this jo Introduction to Botany. means the fruit grower is able to increase very materially the yield of his trees. It seems from observations on dif- ferent forms throughout the plant kingdom that under conditions of good nutrition, if changes occur which check mere vegetative growth, and are not inimical to the life of the plant, then the activity of the plant is apt to manifest itself in the formation of reproductive organs. The results of pruning back branches and roots illustrate this for the higher plants. 53. Position of Buds. Buds usually occur at the apices of branches and laterally in the axils of the leaves ; in the latter position they are termed axillayy, and in the former, terminal. Buds which sometimes occur beside or above the axillary buds are called accessory. Sometimes, how- ever, buds occur without order on both stems and roots, and are then called adventitious. Both axillary and acces- sory buds have the same angular divergence as the leaves, and their growth under good conditions results in a sym- metrically shaped plant. Always many buds are formed which never develop into shoots ; or some, after lying dor- mant for years, may resume their growth if accidents to the plant require the production of new shoots on the old branches. Adventitious buds occur normally on the roots of certain plants, such as the white poplar, but they usually appear only as the result of injuries as illustrated by the numerous shoots which grow forth on the stumps of felled trees. 54. The Nature of a Bud. Whether a bud gives rise to leaves or flowers, or to both leaves and flowers, it is essen- tially a miniature shoot whose succession of internodes, nodes, and lateral outgrowths is but a repetition of a simi- lar succession dating back to the germination of the seed, and constituting the whole above-ground body of the plant. Buds and Stems. We might expect, then, that a bud would have all of the potentialities possessed by the entire plant. How true this is, is shown by the results of the process known as bud- ding, which is practiced by nurserymen for the propaga- tion of various sorts of plants. 55. Propagation by Budding. In this process, a bud, together with the bark and a very thin layer of the wood just beneath it, is re- moved from the plant which it is desired to propagate (a, Fig. 28). A longitudinal slit about an inch long is made in the bark of the plant on which the bud is to be grown, and at the top of the longitudinal slit a cross slit is made so that the bark may be separated from thewood. FIG. 28. Process of Budding, a, cutting the bud from the parent branch ; b, inner surface of the removed portion, showing the base of the petiole, and beneath it a bit of wood adher- ing to the base of the bud ; c, the bud placed in position and partly tied in. After BARRY. The bud is then slipped under the bark and tied into position (c, Fig. 28). After a few weeks the bud will have grown to its foster stem, and the string which binds it down is cut away. This process is usually done in the summer or early fall, and the bud is not expected to grow until the following spring, when all the branches of the foster plant are cut away, and it alone is allowed to develop. The shoot which grows from the bud is found to possess the characters of the plant from which it was taken, and the branches which later spring from it have the same characters. In short, all of the characters of the parent plant were transplanted by means of a single bud ; and so certain is this to occur Introduction to Botany. FIG. 29. a, the root, that the process of budding is relied on for multiplying desirable varieties of many fruits and flowers, such as peaches, cherries, pears, roses, etc. 56. Propagation by Grafting. Likewise, if a small por- tion of the branch bearing a bud. be inserted into the stem of another closely allied plant which is rooted in the soil, after the manner represented in Fig. 29, the correspond- ing parts of the two will grow together, and the branches aris- ing from the bud of the engrafted stem will possess essentially the same characters and bear the same kind of fruit as the plant from which the stem was taken. This process is known as grafting, and is employed in the propaga- tion of various fruits and flowers. We learn from facts of this kind that the powers and quali- ties of the plant as a whole reside in very restricted parts of it ; a fact of great importance to organisms which can- not seek shelter against the vicissitudes of weather, but must stand in one place and meet the force of storms, often with the result of mutilation or even amputation of their members. It is in virtue of this fact that all of the above-ground parts of certain plants, such as Solomon's seal, goldenrod, and Dahlia, may die away and be regen- erated on the return of spring from the relatively small underground portions. 57. Functions of Stems. While a typical stem stands erect above the soil and, for its chief function, bears leaves and connects them with the roots, yet, in the economy of the plant, stems may have other forms and perform other Process of Grafting, and b, the branch, made ready for grafting ; c, grafted root and branch. After BARRY. Buds and Stems. 73 services. The tuber of the Irish potato, for instance, is a portion of a stem having for its chief function the storage of materials; the stems of cacti are green, and perform the food-producing functions; the underground stems of Sagittaria and goldenrod creep along under the surface of the ground, producing new erect shoots here and there, and so serve the purpose of multiplication ; the tendrils of the grape and Virginia creeper, which seem to be stems, have a supporting function. Indeed, as we shall learn in the chapter on modified parts, the members of the plant body may be put to quite as various services as the economy of the plant may require. 58. Habits of Stems. The typical foliage stem is erect or nearly so, and stands by its own strength. Climbing plants do not possess the strength nor form of stem to en- able them to acquire the erect position without the aid of some support. An examination of the structure of stems of climbing plants reveals the fact that they are relatively lacking in the strengthening elements, while the tubes for conducting water occupy a correspondingly larger space. This is what we should expect, for plants that have ac- quired the habit of clinging to other objects for their sup- port have less need of strengthening elements, while their long and slender stems, which lift the foliage to a con- siderable height above the ground, require that a relatively large space be given over to highways for water transport. At the opposite extreme of habit stand the plants with prostrate stems, such as Euphorbia serpens. These two types of stems, the climbing and the prostrate, between which all degrees of gradation may be found, are adapted to quite different habitats, the climbing stems to shady situations, such as dark woods, or the shady side of banks or buildings, and the prostrate stems to situations along 74 Introduction to Botany. the borders of roads, and rocky and waste places, where they may be rooted in good soil, but are able to run out over the barren areas where their leaves will not be too much shaded by the surrounding vegetation. 59. Characterization of Stems. When we survey their character and functions, we find that stems are members of the plant body which bear the leaves and roots, and have for their chief functions the exposure of the leaves to the light, and the transport of materials between the leaves and roots. The other functions which they perform seem to be adaptations to special conditions. CHAPTER V. LEAVES. PROVIDING MATERIALS. Most of the observations on leaves are best made in the field or upon materials freshly brought into the laboratory. If vegetation out of doors is not sufficiently advanced to begin the study of leaves as soon as the work on buds and stems has been completed, the study of modified structures outlined in a following chapter might next be taken up, and the study of leaves postponed until the right kind of material can be obtained in abundance. OBSERVATIONS. In the study of leaves, make account by notes and draw- ings of the following points : 73. The form of the leaf and the character of its outline. 74. The texture of the leaf and the character of the two surfaces, whether rough, smooth, hairy, etc. 75. The manner of attachment of the leaf to the stem; namely, is it broad or narrow at the base ? Is the leaf blade attached to the stem, or does a leaf stalk or petiole intervene ? Are there lateral outgrowths at the base of the leaf ? 76. How does the leaf vary as it grows from the bud ? Do the form and size of the leaf and the character of the two surfaces vary materially ? Compare the color of leaves which are just issuing from the bud with that of mature leaves. 77. How do the leaves vary in form, size, and outline 75 76 Introduction to Botany. from the base to the summit of the stem ? Draw types of the different kinds. 78. How does the angle made by the leaf with the stem vary as the leaf advances from its embryonic condition in the bud to maturity ? Does the direction taken by the stem seem to affect this angle ? To answer this question study the approximately horizontal and vertical branches of the same plant. 79. What is the position taken by the leaves with refer- ence to the incident light ? Note the position of leaves at different times of the day to find out whether the movement of the area of greatest light from the east toward the west affects the positions of leaves, and if so, to what degree. 80. Determine the angular divergence of the leaves. (See page 48.) 8 1. Is there any relation between the breadth of the leaves and the number of vertical rows on the stem ? When the vertical rows are numerous, are the leaves more narrow as a rule than when the rows are fewer ? 82. Is there any definite relation between the lengths of the leaves and their vertical distances apart? It should be remembered that short leaves will permit the light to strike between them better than long ones. 83. When leaves are growing close together in the form of rosettes, how are they prevented from shading each other too much ? Notice whether there is a difference between the lower and upper leaves as to their size and shape, and their angular deviation from the horizontal. 84. In trees and shrubs, do the leaves on the horizontal branches grow from buds on the lower as well as on the upper side ? Do the leaves seem to assume a definite position with reference to the light from above ? Leaves. 77 85. Is there any marked difference in position and dis- tribution between leaves on horizontal branches and those on vertical branches ? 86. Make a longitudinal section with a sharp knife through the middle of a leaf and the branch which bears it, and note its connection with the bark and wood. Re- move another leaf from its stem, with a downward pull, and examine the wound with a lens to see whether the broken ends of the vascular bundles can be made out. 87. Make drawings to show the course of the veins in a grass or lily leaf, or in the leaf of any monocotyledonous plant; also drawings of veins in the leaf of a sunflower, castor bean, or other dicotyledonous plant. Bleach any thin leaf by soaking it in strong alcohol until the chlorophyll is extracted (chlorophyll is the green coloring matter in the leaf), and allowing it to lie in a saturated solution of chloral hydrate (see page 381) for several days ; then mount it in a drop of dilute glycerine, and examine under the medium power of a compound microscope in order to note the ultimate branches of the veinlets. 88. Cover rapidly growing plants or branches of plants so as to keep them dark, and compare the color and size of the leaves which develop in the dark with that of leaves grown under normal conditions of illumination ; compare also the lengths of the internodes formed in the two cases. How long does it take for the blanched leaves to turn green after they have been exposed to the light? Boil for a short time in water a blanched leaf which has devel- oped in this dark and a green leaf which has grown in the light, and place in alcohol until the green leaf has become colorless; then place both leaves in a solution of iodine, and note whether one is colored more purple than the other, indicating a greater amount of starch. Sugars, as 78 Introduction to Botany. well as starch, are manufactured within the leaf ; but the starch is more readily demonstrable, and will therefore be considered here and in the discussion as the visible product of the leaf's work. 89. Make thin cross sections of a green leaf and mount them in a drop of water under a coverglass and study them with a high power of the microscope. Note the rounded green bodies, termed chloroplasts, lining the walls of the cells. Mount other sections under a coverglass in a drop of a saturated solution of chloral hydrate to which has been added sufficient iodine to give it a pale brown color. By this process the leaf will be bleached and rendered transparent, while the starch grains in the leaf will be stained purple. Watch the action of this reagent from the beginning, and note how the chloroplasts are gradually bleached, while the starch grains in them become more and more distinct. Treat in this way sections from a leaf taken just before sunset, and from another leaf from the same plant taken just before sunrise the next morning. Note the relative amounts of starch in the two sections. What conclusions do you reach from the results of your observations ? 90. Tie a branch of a floating water plant, such as Cera- tophyllum or Myriophyllum, to a glass rod or tube and set in a beaker of water, the glass rod being about an inch shorter than the depth of the water. Invert a test tube of water over the rod and plant, the cut end of the plant being uppermost and extending into the test tube. Prepare two other branches in the same manner, filling the second tube with water which has just been boiled and cooled, and the third with water which has been charged with carbon dioxide by blowing into it for some time through a glass tube ; invert each tube in a beaker containing the same Leaves. 79 kind of water that the tube holds. Expose all three prepa- rations to the full light of the sun. Compare the results with those obtained from a single plant placed successively under the three sets of conditions. The first tube and beaker will contain a moderate amount of carbon dioxide, the second little or none, and the third a great deal. Watch for bubbles of gas issuing from the cut ends of the branches. Count the number rising from each in a given unit of time. The green leaves are taking carbon dioxide from the water and are dissociating the carbon and oxy- gen, retaining the carbon for the manufacture of starch, and liberat- ing part of the oxygen. The fre- quency of bubbles in each tube is an indication of the relative amounts of starch manufactured. Set the tubes in the shade and note the effect. What do you learn from these experiments as to the con- ditions necessary to the manufac- ture of starch in the leaves ? Nearly fill a glass funnel with shoots of Ceratophyllum, Myrio- phyllum, or other suitable water plant, and invert it in a tall beaker of well or spring water. The end of the stem of the funnel should be submerged for an inch or more. Fill a test tube with water and invert over the funnel (see Fig. 30). Set the preparation in the sunlight. If the tube becomes nearly half filled with gas, carefully remove the tube from the funnel, close the tube tightly with the thumb, while its mouth is kept submerged ; turn its mouth upward, remove FIG. 30. Device for collecting the gas evolved by a green plant un- der the influence of the sun- light. See text. 8o Introduction to Botany. the thumb, and quickly thrust a glowing, but not blazing, splinter into the tube. The splinter should blaze up, indi- cating the presence of a large percentage of oxygen. 91. Place a bell jar over any plant of proper size grow- ing out of doors, having first fitted a piece of oilcloth, by cutting a slit in it, closely around the base of the plant, and having closed the slit with vaseline so that the mois- ture from the ground will be prevented from rising into the bell jar. Set another bell jar beside the first, on a piece of oilcloth, but not over a plant. After a time compare the amounts of moisture which have been condensed on the inner surfaces of the jars. What does this teach as to the transpiration of water from the leaves ? 92. Mount a small piece of a leaf, with the under side up, in chloral hydrate-iodine (see page 381), and examine with a high power of the compound microscope. By care- fully focusing on the upper surface of the mount, the sto- mata (see page 86), or openings in the epidermis, can be made out. They are made conspicuous by the starch in their guard cells being stained blue by the iodine, while the other cells of the epidermis are lacking in starch and remain unstained. The opening between the guard cells allows carbon dioxide to enter the leaf readily, and oxygen to pass out. It also permits the water to evaporate from the leaf. 93. To determine whether the stomata are necessary to the ingress of sufficient carbon dioxide for the manu- facture of starch within the leaf. Select a plant, such as the lilac, whose leaves have stomata on the under side only. Keep a branch darkened for a day or two or until the leaves are found destitute of starch by the method described in Observation 89. Coat the under side of some of the leaves with a melted mixture of equal parts of cocoa Leaves. 8 1 butter and wax, and expose the branch to the sunlight until the uncoated leaves are found to contain starch. Then test sections from the coated leaves, and if these are found to be without starch, the inference is well founded that this is due to the exclusion of carbon dioxide by the closing of the stomata by the wax mixture. 94. Strip the leaves from some thrifty plant, and pick off new leaves as fast as formed. Note the result, and tell how the final effect is produced. DISCUSSION. 60. Prominence of Leaves. We have seen that as soon as the seedling appears above the ground its leaves unfold and turn green, and that the subsequent development of the shoot appears to consist mainly in the production of a succession of green leaves arranged in a definite order around the stem. When we look at a plant under normal condi- tions, in the prime of its development, it is the wealth of its foliage which impresses us most. In the whole family of grass plants, with exceptions which do not need to be considered here, the stem is very insignificant compared with the leaves. When we contemplate the billows of leaves in vast wheat and corn fields, and remember the rich har- vests that are to follow, we must be impressed with the supreme value of leaves in the life of the plant and in the production of its seeds. Under normal conditions of mois- ture, etc., we find many plants without stems above the ground, but not without leaves. The superficial evidence is therefore plain that leaves are of paramount value in the economy of the plant. We shall see how true this is when we consider the work done by them. 61. Position of the Leaves. We have observed that the leaves are borne in a definite order on the stem. In 82 Introduction to Botany. the lilac and horse-chestnut two leaves are borne at the opposite sides of each node, each successive node having its leaves at right angles to those of the node next below. In corn and other grasses the leaves are in two opposite rows, only one leaf occurring at each node. In the sun- flower there are five rows of leaves, the rows being 72 apart, and each leaf 142 from the one next below or above it. Numberless examples could be brought forward to show that leaves are arranged in a definite order a fact which of itself suggests that they are important members of the plant body. Not only do they have definite places of origin on the stem, but they grow outward from the stem at some- what uniform angles with the horizontal a fact which may suggest to the student that they sustain important relations with external forces. 62. Light Relation of Leaves. When we stand beneath a tree we can see that the shaded portion of its crown does not bear leaves, but only the better-lighted peripheral por- tion. In carrying out Observation 79 we have noticed that the direction assumed by leaves appears to have some direct relation to the light ; for when the plant has been illuminated more on one side than on another, the direction of those leaves which are still capable of growth becomes changed so as to expose their broad surfaces more nearly at right angles to the greatest incident light. Our experiments have taught us further that starch is formed in leaves ex- posed to the light, but not in those kept in the dark. Finally, when the leaves were stripped from a plant it attempted to produce others, but, being prevented in this, it died. Such observations lead us to the conclusion that the defi- nite arrangement of leaves on the stem and the more or less constant angle which they make with the horizontal are for the purpose of insuring that the light shall be impeded Leaves. FIG. 31. Mosaic of Virginia Creeper leaves. The plant is climbing a wall and the blades of the leaves stand vertically. as little as possible in reaching them, and that in some way the light assists them in manufacturing the starch which is an important food of the plant Having reached this conclusion, we find it all the more interesting to note how the leaves strive to intercept the light which comes their way, and how the form and size of the plant and the disposition and direction of growth of its branches are also adapted to this purpose. The same end is attained in various ways by differ- ent plants. When plants are prostrate on the ground or have grown up over a wall, the leaves spread out more or less horizontally in the first instance, but vertically in the last, and intercept nearly all of the light which falls within the radius of the branches (see Fig. 31). When plants are upright, the tiers of branches and leaves are so separated that the light can strike between them; when the leaves are crowded together in ro- settes, the lower leaves grow out beyond the upper ones and produce broad sur- faces only in the exposed area (see Fig. 32); or, when the FIG. 32. Dandelion plant viewed from above. Leaves in rosettes. 8 4 Introduction to Botany. leaves are borne in whorls at the nodes, the illumination of the lower leaves is brought about by an elongation of the internodes (see Fig. 33). In short, after whatever plan the plant may be built, the exposure of the leaves to the light is always provided for. 63. Sun the Source of Energy. The sun is, of course, the one important source of light which reaches the earth from the out- side universe. The heat and light of the sun are due to the intense energy of motion of its mole- cules ; this is communicated to the ether, which fills interplane- tary space, and in which all ob- jects are embedded. (We do not know what the ether is, but there are good reasons for assuming its presence.) The ether trans- mits the motion communicated to it by the sun with such swift- ness that in 8 minutes the dis- turbance is being felt on the earth, having traversed a distance of more than 93 million miles. The vibrations from the sun are manifest to us as light and heat. Those vibrations which give us the sensation of light succeed each other with inconceivable quickness, ranging from 399 million million to 750 million million per second ; those of less frequency than 399 million million, while not producing light, can be detected by their heating effect. In this way, vast amounts of energy are brought FIG. 33 . Veronica Virginica, showing leaves in whorls separated by long internodes. The leaves in each whorl stand opposite the interspaces between the leaves of the next higher or lower whorl. Leaves. to the earth, it being estimated, for instance, that when the sun is in the zenith the energy communicated by it to the earth's surface amounts to one horse power for each area five feet square. It is impossible to conceive of the amount of energy coming in this way to the leaves of plants over the entire surface of the earth ; but the student will find it instructive to estimate the amount for a single definite field of wheat or corn. 64. The Leaf a Manufac- tory. The leaf intercepts the sun's energy and is en- abled by it to manufacture the starch and other food materials necessary to the life and growth of the plant. We must therefore look upon a leaf as a manufactory which uses energy directly from the sun to do its work. To use economically the energy of the sun directly is, as yet, for FIG. 34. Diagram showing the distance apart of the branches of vascular bundles in the sunflower leaf, as seen when look- ing through a bleached leaf with a medium power. The horizontal line shows A mm. magnified to the same extent as the figure. us an unsolved problem, but plants have solved it for themselves. We must examine the construction of a leaf to see how this is accomplished. We note that a typical leaf is spread out in the form of a flat lamina, which insures the interception of a maximum amount of light, and the ready ingress and egress of gases to and from all parts of the leaf. We have seen in Obser- vation 87 that the vascular bundles ramify throughout the leaf so completely as to bring all parts of it in close com- munication with the water brought up from the roots, and to quickly carry out of the leaf its manufactured products (Fig. 34). And we have further seen by Observation 92 86 Introduction to Botany. that, while the leaf is covered with an epidermis which keeps the water from passing out of it too rapidly, there are openings in the epidermis (called stomata ; singular, stoma) through which gases may pass in and out. (See Fig. 35-) Observations 90 and 93 have taught us that carbon diox- ide is necessary to the manufacture of starch by the leaf, and that if the stomata are artificially closed, starch can- not be produced, although all other conditions may be fa- vorable. From this we may conclude that the stomata are the ways through which the carbon dioxide of the atmos- phere enters the leaf. Thus we see the leaf is well provided for receiving the raw materials upon which it must work. But how is the energy of the sun- light employed in transform- ing the raw materials into the finished food product ? If we strip off a bit of the epidermis, without bringing with it the underlying tis- sues, and hold it between us and the light, we see that a large percentage of the light passes through it ; to such an extent, in fact, that objects may be seen through it. This fact assures us that the light may pass freely into the interior of the leaf. If now we hold an entire leaf between us and the light, we find that by far the larger part of the light has been absorbed by the leaf ; in other words, most of the energy from the sun which FIG. 35. Epidermal cells with heavy outlines. The stomata are the elliptical bodies consisting of two curved guard cells with a narrow opening between. Ends of palisade cells of circular outline are seen beneath the epider- mis. From leaf of Solanum rostra- turn seen from above. Drawn with a camera lucida. Leaves. 87 reaches the leaf has not been transmitted through it, but has been arrested within it and transformed into some other form of energy. This has, in fact, taken place within the chloroplasts, which were seen in Observation 89. It is the green substance, the chlorophyll, which has en- abled the chloroplasts to accomplish this. (See Fig. 36.) 65. Starch the First Visible Food Product. We have seen by Observation 89 that starch is formed within the chloroplasts, and we must conclude that the water from the soil and the carbon dioxide of the atmosphere are broughtHogether in them, and that the chloroplasts, em- ploying the energy of the sunlight, transform these sub- stances into the finished food product in the form of starch. We know that starch contains exactly the chemical ele- ments furnished by water and carbon dioxide, and that hydrogen and oxygen exist in the same ratio in starch as in water. The chemical formula for starch is C 6 H 10 O 5 , while that of water is H 2 O, and of carbon dioxide CO 2 . The combination of water and carbon dioxide into starch might be expressed theoretically in the following formula: 5 H 2 O + 6 CO 2 = C 6 H 10 O 5 + 6 O 2 ; the oxygen being given off to the air again through the stomata. Doubtless the process is not as direct and simple as this (it is not definitely known what the steps in the process are), but the equation shows what excellent raw materials water and carbon diox- ide are for the production of starch. 66. The Chloroplasts. The chloroplasts (see Observation 89) are parts of the protoplast and are, of course, alive. It is their special function to arrest the energy of the sun- light, by means of the chlorophyll which they contain, and employ it in the manufacture of plant food from the raw materials, carbon dioxide and water. If Observations 89 and 92 are carefully made, it will be seen that the 88 Introduction to Botany. chloroplasts lie within cells and close against their walls, and that for the circulation of air there are spaces between the cells which are in communication with the stomata. A reference to Fig. 36 will show the relation of the chloroplasts to the rest of the leaf structure. The cells of the upper side of the leaf, termed the palisade cells, are set up in regular order with their long axes parallel to the direction of the incident light ; the chlo- roplasts are embedded in the living substance of the protoplast which lines the cell walls, the remainder of each cell being filled with a wat- ery cell sap. The palisade cells are not compacted together, but have air spaces be- tween them communicat- ing with the stomata. FIG. 36. Cross section of a leaf. /, upper epidermis ; m, stoma in upper epidermis ; n, row of pali- sade cells containing rounded chloroplasts ; i, lower epidermis; k, stoma in lower epi- dermis ; /, spongy parenchyma cells contain- ing chloroplasts ; /, vascular bundle in cross section ; t and u, intercellular spaces. After SACHS. The more loosely ar- ranged parenchyma cells on the under side of the leaf, called spongy parenchyma cells, also contain chloroplasts, but they necessarily receive less light than those on the upper side and cannot manu- facture so much food. The vascular bundles are seen to lie at the center of the leaf where they can readily com- municate both with the palisade and spongy parenchyma Leaves. 8 9 cells, and so give over to them the water that they bring from the roots, and receive from them the products of their manufacture. Thus we see that the leaf is in reality a factory to which the raw materials are constantly FIG. 37. the essential working parts of a leaf and their relation to each -> r ! the upper epidermis containing one stoma ; S, a sieve tube '! manufactured materials are removed from the leaf; r, a tra- cheal tub-*, tr./f>ugh which water is brought into the leaf; between these tubes iis four palisade cells are shown with chloroplasts (rounded, m bedded iiTthe cytoplasm lining their walls. The downward- pointing irrov ; indicate the light energy which penetrates to and is absorbed by the chloroplasis. The gas interchange of photosynthesis and transpiration is indicated by fie curved arrows. brought, and from which the finished product is as con- stantly being tr? . ported. //* 67. Method of the Leaf's Work. The plan of the leaf and the method of its work will be still better understood by reference to the diagram of Fig. 37. For the sake of simplicity, only a few palisade cells covered by a small portion of the epidermis, and a sieve tube and water tube, Introduction to Botany. are represented in the diagram. The water from the roots ascends the water tubes and passes by osmosis into the palisade cells and mingles with their sap. Since the sap bathes the cytoplasm which lines the cell wall, the water has easy access to the chloroplasts embedded in the cyto- plasm (see page 36). The air with its carbon dioxide enters through the sto- mata and fills the spaces between the palisade cells, and needs only to penetrate through their thin walls in order to come in contact with the chloroplasts. n The energy from the sun is readily transmitted through the epidermis to the chloroplasts, and the work of food making is begun. Under these conditions, the chlof p]asts may be- come filled with starch in the course of an hour (see Fig. 38). The starch, which is the' first food substance formed that can be detected by aid of the microscope, does not long remain in the chloroplasts, but is made soluble, mainly in the form of glucose or grape sugar ; and in this form, or in combination with compounds of nitrogen and sulphur to form proteids, it passes into the sieve tubes, and is carried down the stem and in part into the roots, or up the stem where buds are unfolding or flowers and fruits forming, being drawn from the sieve tubes and used for food wherever it may be needed throughout its course. In the night, when the leaf can no longer obtain energy FTG. 38. Cross -cction through leaf of Melilotus alba taken at sundown. The section has been treated with chloral hydrate iodine, .ind the dark granules in the cells are starch. Leaves. from the sun, the chloroplasts cease to manufacture starch, and, gradually becoming emptied of what they contain, by sunrise may show no further traces of it. Thus they begin each day's work unhampered by the products of their previous labors (see Fig. 39). 68. Manufacture of Proteids. Starch and sugar repre- sent only one class of food materials necessary to the nutrition of plants ; the proteids, which contain nitrogen and sulphur and sometimes phosphorus in addition to the carbon, hydrogen, and oxygen composing starch and sugar, have yet to be accounted for. Proteids can be formed in any of FIG. 39 Cross section through leaf of Melilotus alba taken just before sunrise, treated with chloral hydrate iodine and showing that the starch has been removed during the night. the living cells, and in darkness as well as in light. They are evi- dently formed by the cyjtoplasm of the cells from the elements of starch, combined with the compounds of nitro- gen, sulphur, and often phosphorus, which have been abstracted from the soil by the roots. Since their manu- facture can proceed in darkness, the energy for their production is evidently derived from the oxidation of sugar, and other soluble compounds obtained from the starch. 69. Transpiration, and Evolution of Oxygen. Only a small per cent of the water entering the palisade cells is used in the manufacture of starch, the greater bulk of it being transpired into the intercellular spaces, and passing out of the leaf through the stomata. The openings in the* 92 Introduction to Botany. stomata are exceedingly small, being only about T f^ milli- meter in diameter (see Fig. 35), but this small size is com- pensated by the great number of the stomata, of which there may be, in different plants roughly estimated, from fifty to seven hundred in each square millimeter of epi- dermis. While the water is thus evaporated, the salts, brought into the plant in solution from the soil, are left be- hind in a more concentrated solution, from which they are abstracted as needed, in the building up of new compounds. Oxygen is also given off by the leaf, and, for the most part, doubtless through the stomata; the source of this oxygen is the carbon dioxide which has been worked over by the chloroplasts, for they use only the carbon, and set the oxygen free. Thus, while the daylight is strong enough to furnish the necessary energy, there is a con- stant stream of carbon dioxide into, and of oxygen out of, the leaf ; so that while the plant is forming its food, and its food is likewise our food, it is making the air purer for breathing. The process of starch formation by leaves under the influence of the sunlight is called photosynthesis a putting together by light. The diagram shown in Fig. 42 illustrates the mutual relations of root, stem, and leaf in the absorption, manu- facture, and translocation of materials needed by plants. 70. Respiration. After the sun goes down, photosyn- thesis ceases, and another process is found to be going on in the leaves ; that is, the leaves are taking in oxygen and giving off carbon dioxide ; this they were also doing dur- ing the daytime, but the oxygen evolved by photosynthesis predominates so much that the consumption of oxygen at that time is obscured. We see, then, that the leaves are taking in carbon dioxide and giving off oxygen during the daytime, and are taking in oxygen and giving off carbon Leaves. 93 dioxide all of the time, both day and night. This latter process, called breathing or respiration, is essentially the same in plants as in animals, and is as necessary to the life of the plant as to that of the animal. In the higher plants the oxygen for respiration enters chiefly through the sto- mata and through groups of loosely arranged cork cells, termed lenticels, which break through the epidermis in those parts where cork is being formed near the surface. The lenticels can be seen to good advantage as small rounded or elongated protuberances on many woody branches a year or more old. Since all living cells must respire, intercellular spaces are provided in which oxygen diffuses throughout the plant body. In aquatic plants these spaces are large enough to be seen with the naked eye (see the chapter on Adaptation to Environment). Although plants consume oxygen in their breathing, they give off so much more by the process of photosynthesis that the net result is a large addition of free oxygen to the atmosphere. While the process of respiration is com- mon to both plants and animals, that of photosynthesis is peculiar to green plants. 71. Supply of Raw Materials. Thus plants make their own food by the wonderful processes of tearing down and building up which take place in the chloroplasts. An im- portant question in this connection is whether there is an unlimited amount of raw materials at their disposal. Water certainly seems unlimited for the larger part of the earth's surface. The necessary salts occurring in naturally rich soils are also practically inexhaustible, although they may not become soluble rapidly enough to satisfy all the demands of agriculture. Carbon dioxide occurs in the atmosphere in very small percentage, namely, between three and four parts in ten thousand of the atmosphere ; 94 Introduction to Botany. and although it is employed by plants in making their food, it is constantly being replenished by the breathing of ani- mals and plants, by the disintegration of plant and animal remains, by volcanic activity, and by the burning of wood and coal. Since carbon dioxide exists in such small per- centage in the atmosphere, vast amounts of the latter must be sifted by the leaf before sufficient carbon can be ob- tained to build the body of a good-sized plant. A tree having a dry weight of, say, five thousand kilograms would contain twenty-five hundred kilograms of carbon, and to obtain this, twelve million cubic meters of air must have been deprived of carbon dioxide. The spaces between the cells of the palisade and spongy parenchyma allow a broad expanse of free cell surface for the absorption and giving off of gases, the free surfaces acting much as do the gills of a fish in absorbing the small percentage of oxygen from the water. 72. Action of the Stomata. When there is sufficient light to enable the chloroplasts to do their work, there being at the same time plenty of water in the soil to satisfy the demands from the leaf, the stomata stand wide open (Fig. 40, a) and permit the ingress of carbon dioxide ; but if the water supply is running low so that the plant is in danger of drying up, the stomata close (Fig. 40, b\ even when the leaf is well illuminated. The stomata as a rule close in darkness, but rather from physical than physio- logical reasons. The conditions governing the action of the stomata appear to be about as follows : when the leaf is illuminated, the chloroplasts in the guard cells manufac- ture substances which become dissolved in the cell sap, and so alter its density and constitution. This results in an osmotic inflow from the neighboring tissues, which in- creases the turgidity of the guard cells, causing them to Leaves. 95 stretch and spread apart; but in the nighttime the chlo- roplasts of the guard cell no longer manufacture new material ; the cells accordingly lose their turgidity and are drawn together again by the elasticity of their walls (see Fig. 40). When the soil is dry, and the amount of water rising from the roots is much reduced, the guard cells probably lose water faster than they are able to draw it from surrounding tissues, and so are incapable of ac- quiring the degree of tur- gidity necessary to their opening. From such simple causes as these, the plant may allow the ingress of carbon dioxide when the conditions are such that it can be employed in food making, and may guard against too great loss of water when the supply of it is scarce. 73. The World's Food Supply. When we consider pho- tosynthesis from the standpoint of the world's food supply, it becomes a subject of supreme interest. The entire substance of seeds, tubers, bulbs, and roots, which directly or indirectly constitute the food of mankind, was only a few months past scattered in -the form of water, soil particles, and gases of themmosphere, no amounts of which could keep the world from starvation ; and the continuance of animal life has be&n made possible only through the FIG. 40. a, surface view of an open stoma; , surface view of a closed stoma (after HANSEN) ; c, diagram of a transverse section of a stoma. The light lines in- dicate the closed position of the guard cells and the heavy line the open posi- tion (after SCHWENDENER). 96 Introduction to Botany. intervention of plants. The starch and proteids stored up in seeds, and particularly in the grains of cereals, are in quite stable condition, and are well adapted to carry plant life through months and even years of adverse conditions. Their stability and condensed condition also make them fit for the food of mankind through the months between har- vests and through years of famine. It is this stable and condensed form which enables cereals to be transported to all quarters of the globe so that the people of one conti- nent may be fed from the granaries of another. 74. Amount of Work done by Leaves. The amount of work done by the leaves of plants in a single year over the entire earth's surface is beyond computation ; but perhaps some idea of its immensity may be gained by calling to mind that in the state of Kansas alone, in the year 1900, over 134 million bushels of corn and over 77 million bushels of wheat were harvested. Or, to take examples with smaller numbers, it has been estimated that one square meter of sunflower leaf may, in a single summer day, produce twenty-five grams of starch, and a single stalk of corn may in the same time send out into the ears from ten to fifteen grams of reserve food material. 75. Duration of Work of Leaves. In some kinds of plants, such as tulips, peas, wheat, and corn, the leaves finish their work before the close of the growing season and die, having first given over to the seeds, bulbs, etc., most of their materials which could be used as reserve food. In other plants, such as our common trees and shrubs, the leaves continue their work until the close of summer. They then send over to the body of the plant, which is to survive the winter, much of the useful material contained in them ; and then sever themselves from the branches by producing a layer of delicate tissue, so that Leaves. 97 they become torn away by their own weight, or are easily blown off by the wind. The separating layer of tissue is often of the nature of cork and then serves also to heal the wound. In evergreens, however, the leaves may re- main on the branches for several years. Figure 41 shows a branch of pine bearing leaves some of which are ' three years old. The fall of the leaf is a wise provision for the con- i ditions of winter. When the ground is very cold or frozen, the roots are no ' longer able to absorb FIG. 41. water from the soil, and ...... . . Branch of Pine tree bearing leaves three years it the broad transpiring old . There are gaps between the leaves of surfaces of the leaves re- each y ear>s s rowth where the bud scales were mained, the plant would suffer from too great loss of water ; the weight of the snow also which would accumulate on the leaves would break the branches, as may sometimes be observed when early snows overtake the trees with their leaves still on. 76. Size and Form of Leaves. Leaves show great varia- tion in size and form. The leaves of mosses, for instance, are only a few millimeters in length and breadth, while those of the palm Raphia tcedigera, growing in Brazil, have petioles from four to five meters long and leaf-blades from nineteen to twenty-two meters long and twelve meters broad. The student can at any time during the growing season find endless materials for the study of variations in leaf forms. We should not, however, look at the differ- ences in leaf forms as expressions merely of the power to vary, for we may find that the form of the leaf is nicely 98 Introduction to Botany. adjusted to its size, position on the stem, and the habit and habitat of the plant. Indeed, it may be taken for granted that any member of an organism so important to the life of the individual and the continuance of the species as the leaf is would not be apt to show marked variations not in some way correlated with its functions. 77. Characterization of Leaves. While the leaf is an outgrowth from the stem it does not grow indefinitely as stems do, but soon attains its maximum size. It seems impossible to formulate a definition that will clearly apply to all leaves ; as a general characterization we might say, however, that leaves are lateral outgrowths, having buds or branches in their axils, arising in definite succession on a stem, limited in growth, and having for their chief function the manufacture of the plant's food. * Chief functions of the leaf: Photosynthesis. Absorption of gases. Absorption of the sun's energy. Transpiration. Absorbed by the leaf: Sun's energy. Oxygen for respiration. Carbon dioxide for photosynthesis Given off from the leaf: Oxygen from photosynthesis. Carbon dioxide from respiration. Water by transpiration. Important functions of the leaf in common with other plant parts: Synthesis of proteids. Respiration. Digestion. Absorbed by the roots : Oxygen. Water. Salts of: Potassium. Calcium. Magnesium. Iron. Nitrogen. Sulphur. Phosphorus. Given off from the roots : Carbon dioxide. Possibly in some ir stances organic acids and enzymes. FIG. 42. Longitudinal diagram of the vegetative parts of a plant, with special reference to the absorption and translocation of materials. * In this diagram the dotted highway is the water-conducting area (xylem portion of vascular bundle), and the black highway (phloem portion of the vascular 'bundle) is the area for conduction of the food made in the leaf. The arrows indicate the direction of flow in these highways. CHAPTER VI. GROWTH AND MOVEMENT. PROVIDING MATERIALS. For most of the following observations, plants growing under natural conditions out of doors are to be employed. Only those plants should be selected which are thrifty and in a growing condition. In obtaining root tips of onion, place the bulbs on moist carpet or blotting paper, and cover with a bell jar. When the roots have grown out about T 3 6 of an inch, cut them off with a sharp knife and place them in a i % solu- tion of chromic acid in water for 48 hours ; then wash in running water for half a day, and place in 20 % alcohol for a few hours, and for the same length of time in 50 % alcohol, and finally in 70 % alcohol. After being prepared in this way the roots may be kept indefinitely in equal parts of alcohol, glycerine, and water. Good sections for our present purpose can be obtained by embedding the roots in elder pith, and making longitudinal sections free-hand with a sharp razor (see page 377). Thin median sections should be stained in a solution of Safranin (see page 388), and mounted for examination in dilute glycerine. There are more elaborate methods for preparing uniformly thin sections by embedding the material in paraffin, and cutting the sections with a microtome (see pages 383 and 386), but these methods are not necessary for this study, since a few good sections may serve for demonstration to the entire class. In selecting stamen hairs of Tradescantia, only those should be chosen whose cell sap is still colorless. These hairs of different ages might be used in place of sections from the onion root tip, but they are not so satisfactory as well-prepared sections. It is a simple matter to grow seedlings of the sensitive plant, Mimosa pudica, in pots under bell jars. The soil should be a mixture of equal parts of rich garden soil, sifted sand, and well-rotted manure. The pots should be kept in a warm place, and as soon as the seedlings appear, the bell jars should be raised at one side. The pots should be kept well watered. 100 Growth and Movement. 101 OBSERVATIONS. 95. With waterproof India ink make marks two millime- ters apart on some rapidly growing stem, beginning at the apex and extending downward for several internodes. Ob- serve from time to time whether the marks become sepa- rated farther by the elonga- tion of the stem, and whether growth seems to be more rapid in one region than in another. Where does growth in length seem to have ceased? Com- pare with similar observations on the growth of roots. 96. By means of the simple apparatus illustrated in Fig. 43 observe the rate of growth of some rapidly growing stem. Compare the amount of growth in the daytime with that for the same number of hours in the nighttime. 97. By means of recorded measurements, compare the rate of "growth of two plants of the same kind, one of which is in a dry soil, and the other under the same conditions, with the exception that it is kept well supplied with water. What conclusion do you reach as to the use of water in growth ? 98. Cover one shoot of a plant which branches near the ground (such as the potato) with something to exclude the light, and leave the remaining shoots uncovered. After a few days compare the lengths of the newly formed inter- FTG. 43. A simple form of Auxanometer. A thread is attached to the apex of the plant and passed over the pulley and held taut by a weight which is only heavy enough to move the pointer as the plant elongates. The arc can be made of heavy manila paper and all other parts of light wood. 102 Introduction to Botany. nodes of the shaded and unshaded shoots, and also the sizes of the leaves formed after the experiment was started. What is the effect of absence of light on the growth of stems and leaves ? 99. Plant some seeds of Indian corn and garden bean in moist sawdust contained in a wire basket, which should be inclined as shown in Fig. 44. Keep the sawdust moist, and note the direction taken by the roots after they have grown down through the meshes of the wire at the bottom. What does this experiment teach as to the probable behavior of roots under natural conditions ? 100. Bend over a vertical shoot of some thrifty plant, and fasten it down in such a way as to allow freedom of action toward the apex. Observe the position finally taken by the stem and leaves. How do FIG. 44. you account for the change of Experiment to show hydrotropism position observed, and what is its of roots. After SACHS. use 101. Shade a plant so that it receives light on one side only. How do the leaves and stems behave, and to what purpose ? Remove the screen after a marked change has been noticed, and note whether the different members assume their former positions. 1 02. Invert a plant and notice the direction taken by its growing members. Do those parts which have ceased to grow change their positions ? After a day or so set the plant upright and note whether the parts come back to their original positions. 103. Observe the behavior of the tendrils of plants Growth and Movement. 103 growing under normal conditions out of doors. Try to determine what incites some tendrils to twine, and why the tendrils of Virginia creeper grow toward a support. Gently rub the tendrils of squash or wild cucumber on one side with a stick and watch for the result. Inclose some young shoots of Virginia creeper so that they are kept dark, and, after new tendrils have been formed under these conditions, note whether they grow in a different direction from that taken by tendrils which have developed under normal conditions of illumination. 104. Note the positions of leaves of clover, Oxalis, Amorpha, etc., in the daytime and in the nighttime. Of what use are the observed changes in position ? 105. Observe the direction taken by the stems of trumpet creeper. Is there any difference in behavior between those stems which bear leaves only and those which bear flowers as well as leaves ? 1 06. Grow in a greenhouse or under a bell jar seedlings of Mimosa pu^ica, and note the effect of touching the leaf- lets, or of shaking the entire plant. Do the leaflets change their position on being transferred from sunlight to shade, and vice versa ? Do they have distinct positions for night- time and daytime ? Of what use to the plant are the actions observed ? 107. Mount a young stamen hair of Tradescantia Vir- ginica, or hairs from young portions of the stem of tomato or squash, in a drop of water on a glass slip, and examine under high power of the microscope for streaming motion of the cytoplasm. In removing hairs, some of the tissue to which they are attached should be taken with them in order to prevent their injury. 1 08. Cut a hole a trifle smaller than a coverglass in a piece of thick felt paper one inch square. Boil the paper IO4 Introduction to Botany. for a short time in water, and place it at the center of a glass slip. Place at the center of a coverglass a small bit of rotting wood or bark on which is growing a slime mould plasmodium (see page 252). The piece of wood or bark should be so small that it will cling to the coverglass by its own moisture. Put the coverglass with the object down- ward over the hole in the felt paper, and set the prepara- tion over a tumbler of water under a bell jar so that it will not become dry. If the experiment is successful, the plas- modium will grow out over the coverglass, and may be studied by transmitted light under high powers of the microscope. Make notes on the streaming of the proto- plasm. The batter like plasmodium can be found at almost any season of the year under the bark of moist logs or on decaying leaves which have gathered to some depth in damp woods. DISCUSSION. 78. The Plant Cell. When we examine very thin sec- tions of the growing root tip of onion, for instance, under a high magnifying power, we find that they are composed of very small compartments, those near the apex being very nearly isodiametric, while those farther back are more or less elongated (Fig. 45, A and B}. If we were able to see through a whole root tip magnified to the same extent, we should find that each of these compartments is really a closed box to which, including its living contents, the term cell has been applied. The walls of the cells of the onion root tip are composed of cellulose, a substance well suited to form the walls of growing cells, for it can stretch and allow the cells to enlarge, and it permits liquids and gases in solution to pass through it readily. It is not alive, but has been manufactured by the live parts of the cell. The Growth and Movement. 105 live part of the cell consists of the cytoplasm, a proto- plasmic structure which occupies most of the cell cavity of young cells ; the nucleus, which is suspended centrally in the cytoplasm in young cells, but as the cell grows older may have a lateral position (Fig. 45); the leucoplasts, small dense bodies which multiply by division and have special functions re- counted in the next para- graph; and the plasma membrane, a special- ized part of the cyto- plasm which lines the cell wall. (See Fig. 12 for details.) 79. Functions of Cell Organs. The plasma membrane, cytoplasm, leUCODlastS, and nucleus A > longitudinal section through the root tip of an Onion ; B, successively older cells, i, from Constitute the live part immediately back of the root cap where cell of the cell, and whatever d ,j vision g in f on : 2 an 3, older ceils, showing the modifications which I undergoes is done by the plant as with age. In i the cytoplasm fills the cell i -i j cavity and the nucleus is relatively large. The a living body is accom- few h y eavy points indicate leucopksts plished by one or more of these live parts or organs of the cell, which collectively are termed the protoplast. We have noticed in our study of roots that it is the plasma membrane which determines, to some extent, whether certain substances shall pass to or from the interior of the cell. It seems to be the guardian of the cell and the inspector of all material interchanges. It appears also to build the cell wall, and there is evidence to show that it is the receiving organ for stimuli from the FIG. 4S . 106 Introduction to Botany. outside world light, heat, gravity, mechanical impact, etc., being probably first perceived and communicated by it to the other organs of the cell. TJie^cytoplasm is the medium of interchange of stimuli between the plasma membrane and^the nucleusj it prob- ably manufactures various nitrogenous food materials from substances furnished it by the chloroplasts, and from salts of nitrogen, sulphur, and phosphorus, which have come up from the soil. It appears to have something to do with the production of ferments which render the reserve food materials more soluble and diffusible ; it is probably con- cerned with manifold changes of a chemical nature which are constantly taking place within the cell; and it con- tributes some of its own substance toward the production of certain fibrillar structures which assist in nuclear and cell division. The leucoplasts have the power of forming starch from materials which come to them from the leaves ; or when they are exposed to the light they may produce chlorophyll within themselves, and become chloroplasts ; or they may produce other coloring substances than green, as seen in certain flowers and ripening fruits, and then they are termed chromoplasts. Leucoplasts, chloroplasts, and chromoplasts collectively are called plastids. To the nucleus, in particular, is intrusted the very impor- tant function of bearing and bequeathing from generation to generation the inheritable qualities. That the embryo in an acorn shall develop into an oak instead of into an- other kind of plant depends in large measure on the nuclei in the cells of the embryo. The nuclei, as the bearers of the inheritable qualities, must determine how the cells shall behave under varying conditions. The nucleus has to do also with processes involving chemical changes, such as the Growth and Movement. 107 formation of starch and proteids, the production of secre- tions, the growth of plasma membrane, and building of cell wall. While it is not absolutely known that the parts of the cell have the distinct functions here assigned to them, yet the circumstantial evidence that they do amounts almost to proof. We find, then, that we may look upon the living cells of the plant body not only as units of structure, like the bricks of a house, b,ut as centers of vital activity which induce and regulate whatever the plant does. 80. Advantages of Cellular Structure. The construction of the plant body from many small cells has certain distinct advantages : it renders the body stronger, lessens liability to fatal injuries, and makes division of labor possible, so that one part of the body may protect the other parts; one part may give strength to the whole body, while other parts may be adapted for transporting or manufacturing materials, etc. Thus the business of the plant is economi- cally and efficiently carried on. 81. Continuity of Living Substance. While the live part of the plant body seems to be divided by the cell walls into numberless units, it is probable that these are united by minute strands of living substance, which are difficult of demonstration by means of the microscope; their existence, however, has actually been demonstrated in many cases. We are justified in the conception that the whole live body of the plant stands united by living substance, from the farthest roots to the remotest buds, although apparently severed by numberless cell walls. 82. Cell Division. Tne enlargement of the plant body depends upon the multiplication and enlargement of its cells. Multiplication of the cells is brought about by their division, one cell becoming two by the formation of a new io8 Introduction to Botany. partition wall, and so on. In this process the parent cell must distribute to the two daughter cells resulting from its division all of the qualities and powers possessed by itself ; and to accomplish this it is important that the division of the nucleus in particular should be equal, one daughter cell receiving neither more nor less than the other. We are able to see, in following the steps in the division of a cell, that the equal partition of the nucleus is actually accomplished with astonishing care (see Fig. 46). The' nucleus becomes threadlike in structure (i); the thread is divided longitudinally through the middle, and then the double thread is broken transversely into several double rods (2); the double rods are now grouped at the equator of the cell, namely, at the central plane, where the dividing wall is to be formed (3 and 4) ; then the two halves of each double rod are drawn apart to opposite poles of the mother cell (5, 6, and 7), where they fuse together to form two daughter nuclei (8). Finally a wall is formed which cuts the mother cell into two daughter cells (8 and 9). This will serve as a general statement, but the details of the process are so wonderful that they have been given more fully in the description of the figure. If we go back to the beginning in the life history of one of the higher plants, we find that it is, at first, a fertilized egg cell, of which we shall learn more in the chapter on the flower. The plant has, therefore, its beginning in a single minute cell ; this divides, and its offspring in their turn divide, until the whole plant body, consisting of mil- lions of cells, is formed by its descendants. 83. Cell Growth. After the cells have divided, the daughter cells increase in size, and not till then does an enlargement of the plant take place. The increase in size of the cells is brought. about by absorption of water until Growth and Movement. 109 8 FIG. 46. Diagrammatic representation of Nuclear and Cell Division. 1. A cell with resting nucleus just previous to division. The cytoplasm (stippled) fills the cell cavity. The nuclear thread is shown as a tortuous band throughout the nucleus; the black body in the nucleus is the nucleolus. 2. The nuclear membrane and the nucleolus have disappeared, the nuclear thread has become divided transversely into distinct bodies termed chromosomes, and these are seen to be divided longitudinally. 3. The chromosomes have become lined up at the equator of the cell and pro- toplasmic threads converge from them toward opposite poles. 4. The same as 3 seen from one of the poles. 5. The longitudinal halves of the chromosomes are moving toward opposite poles. ^ 6. A later stage, showing connecting protoplasmic threads between the receding chromosomes. 7. The chromosomes arrived at the opposite poles are fusing together end to end to form nuclear threads. 8. The nuclear threads have assumed the form of two daughter nuclei, nucleoli have appeared, the connecting threads have spread from wall to wall, and a new cell wall dividing the mother cell in halves is being formed, apparently by the con- necting threads. 9. A nuclear membrane has been formed about the daughter nuclei, the con- necting threads have disappeared, and nuclear and cell division is completed. no Introduction to Botany. the walls become stretched, by the laying down of new materials in and about the walls, and by the addition of appropriate materials to the different parts of the proto- plast. The addition to the cell wall is evidently accom- plished by the plasma membrane, while each part of the protoplast is presumably capable of assimilating materials for itself. We see how necessary water is to growth, not only in giving up its hydrogen and oxygen for the manu- facture of plant substance, or in acting as a solvent, but in supplying the necessary stretching force which initiates the first step in increase in size. 84. Changes in Character of Cells. As the cells attain their definite size and form, we find that they do not all behave in the same manner, although they have all de- scended from a common parent cell. Some become long and fibrous, while others remain nearly isodiametric ; some fuse end to end to form water tubes, while others infiltrate their walls with waxy substances to keep water from pass- ing through them. The cells have come to act so differently because they have been under different conditions. Those which are on the outside exposed to the air have not the same surroundings as those which lie at the interior, and the various zones of interior cells are under different con- ditions of exposure to air, and of tension, pressure, etc. Thus the unlike action of cells which have descended from a common ancestor may be in part acounted for. 85. Regions of Continued Growth. In dicotyledonous plants, such as the oak, maple, elm, etc. (B, Fig. 47), the regions of continued growth lie at the apices of roots and shoots, in the cambium zone which separates the bark from the wood, and in certain zones of cells called cork cambium which give rise to the cork of the bark. In monocoty- ledonous plants, such as grasses (A), palms (C), etc., there Growth and Movement. in is no cambium zone similar to that in dicotyledonous plants ; but in such monocotyledonous plants as the palm and smi- lax (C) a zone of cells near the periphery of the stem remains in a dividing condition indefinitely, and thus adds to the diameter of the stem, some of the cells of the periph- FlG. 47. Diagrams showing regions of continued growth in dicotyledonous and monocoty- ledonous plants. The shaded regions are capable of growth. A, a Monocoty- ledon of the grass type, growth taking place at the apices of the stem and roots and at the bases of the younger nodes ; C, a Monocotyledon of the palm and lily type, the apices of the stem and roots and a zone (/) near the periphery being in a growing state; B, a Dicotyledon, growth taking place at the apices of the stem and roots and at the cambium ring (z). eral zone undergoing the necessary modifications to form new vascular bundles. In such monocotyledonous stems as those of grasses (A), increase in length is also brought about by the division of the cells at the base of each node, which retain the power H2 Introduction to Botany. of division for a long time. It is a matter of common observation that grass stems are easily pulled apart at the nodes, and that the place of rupture is tender, succulent, and sweet ; these are all characteristics of regions where cell division is rapidly going on. The tender bases of the nodes of grass stems are strengthened by being enwrapped by the bases of the leaves. In the leaves of grasses, and in all leaves which become much elongated, or which spring from underground bulbs, etc., division of the cells of the basal portion continues for some time ; but leaves in general owe their growth mainly to the enlargement of the cells which constitute them in their embryonic condition in the bud. In some plants, the elongation produced by the division of the cells at the apex is continued indefinitely through the growing season, as illustrated by roses and morning-glory, while in others the elongation of the shoot soon ceases with the formation of a winter bud, as shown by the hickory and horse-chestnut. 86. Phases of Growth. Observation 95 has shown us that the region of greatest elongation is a short distance back of the growing apex; this is the region where the daughter cells, produced by cell division, are increasing in size. Back of this region, elongation has ceased, and thick- ening of the cell walls and changes in their chemical con- stitution and in the condition of the protoplasts are taking place. We might, therefore, speak of three phases of growth: (i) the phase of cell division; (2) the phase of cell enlargement; (3) the phase of cell modification. 87. Conditions Necessary to Growth. The conditions necessary to growth are essentially the same as those requi- site to the germination of seeds, which is, in reality, simply a resumption of growth. Water must be at hand in suffi- Growth and Movement. 113 cient quantity to render the cells turgid ; food materials must be available ; there must be a certain amount of exter- nal energy in the form of heat ; oxygen must be present for the process of respiration, resulting in the setting free of internal energy, without which the life of the plant would become extinct; finally, there must be an inclination to cell division. This last condition is itself dependent, to FIG. 48. A, a shoot of Virginia creeper growing in the light. B, a shoot from the same plant growing in partial darkness. a certain degree, on the others ; but, even when these are favorable, the inclination to cell division does not always result, as we see in the cessation of growth of hickory shoots in the height of the growing season, and in the limited growth of embryos in forming seeds. The causes for this behavior are inherent in the nature of the cell, and are faithfully transmitted by cell division from generation to generation. H4 Introduction to Botany. 88. Influence of Light and Gravity. While light and gravity are not necessary to the immediate processes of growth, they do influence the direction and character of growth of the plant members, as we have already seen. Light has much to do with the size and form of the mem- bers. Compare, for instance, a shoot of Virginia creeper which has grown in the dark with one which has grown fully exposed to the light (Fig. 48). We see in such a case that the internodes of the shoot which has grown in the dark are much longer than those of the shoot which has developed in the light, while its leaves are considerably smaller than those of the illuminated shoot. We can see the usefulness of the habit of greatly elongating inter- nodes and keeping the leaves reduced where the shoot is in much darkened places, for where the leaves cannot have access to the light they require materials for their production which they cannot replace by the manufacture of food materials. The greater elongation of internodes in the dark brings the leaves more certainly and quickly into illuminated places. 89. Rings of Annual Growth. When a perennial di- cotyledonous plant resumes growth in the spring, it pro- duces more branches and leaves than it possessed the pre- vious year. This is characteristic of branching perennial plants. In consequence of the increased transpiring sur- face and weight of the crown, more demands are made on the stems and roots, for they must be, stronger, and they must be able to conduct larger supplies of water to the leaves. Here is where the usefulness of the cambium ring is shown ; for while the leaves and branches are being formed, the cells of the cambium ring are dividing and adding to the thickness of the stems and roots. The tis- sues which are first formed by the cambium are of a nature Growth and Movement. to meet the most pressing demand at the time ; namely, for a greater water supply for the increased transpiring sur- face of the leaves. Accordingly we find that a great many water tubes are first formed (see Fig. 49), which com- municate with the veins of the leaves and with the water tubes running out into the newly formed rootlets. The water supply having been provided for, the cam- bium cells next produce wood fibers in much greater pro- portion. At the close of* the season we find on examining the year's growth that it con- sists of a zone of tissues (s) in which the water tubes pre- dominate, followed by a zone (/) which is more dense and firm because the water tubes in it are smaller and fewer, and the thick-walled wood fibers more in evidence. A single ring of annual growth consists then of a zone of early growth and a zone of later and denser growth, each zone having its own peculiar significance in the economy of the plant. The cambium ring makes annual additions to the bark as well as to the wood, but in much less quantity, and the additions are not demarked into rings of growth. 90. Plants without Annual Rings. In perennial mono- cotyledonous stems, which branch but little or not at all, the crown of leaves does not increase materially from year FIG. 49. Constitution of a ring of growth, s and u, early growth ; t, late growth. The lowest row of small cells in s belongs to the late growth of the previous year. The early growth here con- sists chiefly of the tracheal tubes and wood parenchyma and the late growth chiefly of wood fibers, s and t constitute an annual ring. After HABERLANDT. FIG. 50. FIG. 51. FIG. 52. FIG. 53. Fig. 50. Castor bean grown under equilateral illumination. Fig. 51. The same plant after some hours of slow revolution on a universal axis. Fig. 52. The same plant after a few hours of equilateral illumination, following the condition shown in Fig. 51. Fig. 53- The same plant after a few hours of one-sided illumination, following the condition shown in Fig. 52. <^JJ^_^ **^K rv FIG. 54. FIG. 55. FIG. 56. FIG. 57. Fig. 54. The same plant after a few hours of equilateral illumination, following the condition shown in Fig. 53. Fig. 55- Another castor bean plant grown under equilateral illumination. Fig. 56. The same plant as shown in Fig. 55 after being inverted for a few hours under equilateral illumination. Fig. 57. The same plant after being set erect for a few hours under equilateral illumination, following the condition shown in Fig. 56. n8 Introduction to Botany. to year, and new additions to the water-conducting ele- ments and to the strengthening elements are not so neces- sary as in the case of branching dicotyledonous stems. Accordingly, we find that most monocotyledonous stems increase but little in thickness, and give no evidence of rings of annual growth, since the bundles are scattered, and there is no true cambium ring. The grass stem, which represents in its general structure a vast number of endoge- nous stems, is a marvelous example of architectural achieve- ment, for its height is often five hundred times its diameter. If Washington Monument were built in like proportions its base would cover an area of less than one square foot. Stems of this sort, which increase but little in diameter, show us how perfectly plants are constructed from the purely mechanical standpoint. 91. Sensibility of the Protoplasts. One of the most re- markable things about the live part of the cell, namely, the protoplast, is its sensibility to its surroundings, and its capacity to respond in certain definite ways to varying external conditions. The polarity of plants, as we see it exhibited in root and shoot, is an expression of this sensi- bility, since the protoplasts of the cells of the root use gravity to guide their part of the plant body downward, while those of the shoot find the upward direction by the same force. The stem of the trumpet creeper finds its way to a support through the perception of light, while the leaves are directed away from the support and toward the light by the same means. If, by any accident, a plant becomes overturned or bent out of its normal position, the protoplasts perceive the altered relation to light and gravity, and cause the growing members to shift their positions into proper relations to these forces. Figure 50 is a photograph of a young castor Growth and Movement. 119 bean plant which has been grown in a pot, and kept equally illuminated on all sides. Figure 5 1 shows the same plant after revolving for eighteen hours on both horizontal and vertical axes at the same time, so that both light and gravity as a guide were useless to it. Its protoplasts ap- pear to have perceived its abnormal condition, and have changed the position of the leaves ; having no guide, how- ever, only fruitless curvatures have resulted. Figure 52 represents the same plant after standing eigh- teen hours in a normal position under equilateral illumina- tion ; the protoplasts have found their direction again, and have placed the leaves more nearly in their wonted position. Figure 53 represents this plant after being next illuminated on one side only for twenty-four hours ; the protoplasts of both stem and leaves have attempted to bring the leaves into position for receiving as much as possible of the inci- dent light. Figure 54 shows the same plant again after being equally illuminated on all sides for about twenty- four hours ; since there was the same degree of light intensity on all sides, gravity has evidently been em- ployed to bring the parts back from their one-sided position. Figure 55 is a photograph of another plant which has grown in a pot under normal conditions. Figure 56 repre- sents the same plant after standing inverted for about eighteen hours while kept equally illuminated on all sides by rotation on a vertical axis ; a very successful attempt has been made to bring the leaves and stem back to their normal relations to light and gravity. (To see this to best advantage hold the book upside down.) Figure 57 shows the same plant again after standing erect under equilateral illumination, the stem and younger leaves having assumed approximately their original positions. I2O Introduction to Botany. 92. Greater Sensibility of Growing Members. In com- paring these photographs, it is seen that the younger portions of the stem and the younger leaves are more responsive to the reversed position or to unilateral forces. It appears that, in the older members, the protoplasts may be less sensitive to external forces, and that it is a more difficult matter for the older and somewhat rigid parts to change their positions. 93. Cause of Movements. The movements which we have just observed are due to a more rapid growth on one side of the leaves and stem than on the other. When the plant is inverted, the cells on the lower side of the petioles and leaf blades and on the lower side of the stems increase in size more rapidly than those of the upper side, and there is accordingly a general bending of these parts upward. When the plant is illuminated on one side more than on another, growth is most rapid on the side remote from the source of greatest illumination. When a plant which has made a one-sided growth under such circumstances is again placed so that it is equally illuminated on all sides, its parts draw back toward their normal position, provided they are not too old for growth ; but in order that this may occur, growth must take place on one side more than on another, although all sides are now equally illuminated. It appears that in such cases gravity is used as a guide, and that the protoplasts persist in causing unilateral growth until the stems and leaves stand in their normal positions. The experiment illustrated in Fig. 51 is very instructive, for it teaches that when the directive influence of all ex- terior forces is removed the protoplasts are no longer able to determine a definite position for the stems and leaves. 94. Heliotropism. As we have seen in the study of leaves, the interception of sunlight is of vital importance Growth and Movement. 121 to plants, and therefore light is the most fea- sible guide in determining the position of leaves and leaf-bearing branches. Since, however, the source of great- est illumination hourly changes as the sun ad- vances from east to west, it is plain that if the posi- tion of leaves is fixed once for all, the best possible light relation is not attained. The behavior of a rapidly grow- ing sunflower shows how plants may take account of the shifting light. The three photo- graphs of Fig. 58 show the same plant as it ap- peared in the 122 Introduction to Botany. morning, at noon, and in the late afternoon of a single day. It can be seen, by comparing the same leaves in the different photographs, that they were incessantly striving to intercept as much light as possible by keeping their broad surfaces at right angles to the changing direc- tion of greatest illumination. Such movements, and any others caused by light, are designated as heliotropic, and the state or condition of plants which makes heliotropic movements possible is termed heliotropism. The student may observe many other plants which exhibit high degrees of motility of this kind. 95. Influence of Various Forces. The movements ex- hibited by plant members, for which light and gravity are the guiding forces, are of the most vital significance to the plant; but there are movements which are directed by other means. Observation 99 has taught us that roots may disregard gravity and turn in the direction of moist areas; and we saw by Observation 103 that by contact with an object, tendrils of some plants may be made to grow on one side more than on another so that they twine about the object if it is of suitable size and shape. There are other movements due to unequal growth, exhibited chiefly by the parts of flowers, which are induced by vary- ing degrees of light and heat. The flowers of Tulip, Crocus, Colchicum, etc., will open in a few minutes if the tempera- ture is raised to a marked degree, and at a constant tem- perature they will open in the light and close in the dark. It is a matter of common observation that the dandelion behaves in this way. 96. Motor Organs. Old plant members which exhibit movements are usually provided with special structures for that purpose. A description of the behavior of the leaves of scarlet runner, and of their motor organs, will serve to Growth and Movement. 123 illustrate this. Figure 59 represents a leaf in its night posi- tion; at a, b, and c (Fig. 60) are the motor organs. The posi- tions of the motor organs of the leaflets are shown for the nighttime at B, and for the daytime at A. Cross sections of a petiole and of a motor organ are shown at C and D. It is seen that while the petiole is made rigid by the disposition of its vascular bun- dles in a circle outside the cen- ter, as seen at C, and by the wing- like outgrowths containing each a vascular bundle g, the vascular bundles in the motor organ are all thrown to the center; and surrounding them is a relatively broad zone of thin-walled parenchymatous tissue which is capable of undergoing great variation in the turgidity of its cells. In the nighttime the upper portion of the paren- chymatous tissue of the motor organ of the petiole becomes less turgid than the under portion, and the leaf as a whole rises in consequence ; but at the same time the motor or- gans of the individual leaflets become less turgid on the under side, and the leaflets are made to droop. In the daytime the motor organs of the leaflets become less turgid on their upper sides, and the leaflets rise in consequence, while the motor organ of the petiole becomes less turgid on its under side and the leaf as a whole drops to a lower plane. FIG. 59. Leaf of Scarlet Runner in its night position. After SACHS. I2 4 Introduction to Botany. Such movements are in harmony with the functions of the leaf, for the leaflets are spread out to receive the light necessary to photosynthesis in the daytime, and are folded together in the nighttime so that they are less apt to receive injury from too great radiation of heat or from the beating of storms. The variations in the turgidity of the motor organs are induced and regulated by the proto- plasts, which are influenced in their action by variations in FIG. 60. Motor organs (a, b, and c) of Scarlet Runner in their day position at A, and in their night position at B. C, a cross section of a petiole, and D of a motor organ. After SACHS. light intensity. Periodic movements induced by alterna- tions of day and night may be observed in the oxalises (commonly represented by the violet and yellow wood sorrel) and in many members of the pulse family. 97. The Sensitive Plant. Movements of the leaves of some plants may be induced by contact with a solid body, by shaking the entire plant, by intense illumination, or by chemical stimulus, etc. The sensitive plant, Mimosa pudica, Growth and Movement. 125 affords a most no- table example. Figure 61 shows photographs of a seedling of this plant under dif- ferent conditions : A represents the plant in diffuse light, with its leaf- lets spread out to catch the light ; B shows the leaf- lets somewhat folded together as the result of a short exposure to direct sunlight ; in this position the leaflets stand more nearly paral- lel with the inci- dent light ; C ex- hibits the plant directly after being shaken by a strong wind. Figure 62 rep- resents a leaf of a mature sensitive plant in its open position at A, and in its closed posi- 126 Introduction to Botany. tion at B, after being touched or shaken. If one of the leaflets of the upper pair be lightly touched, it will rise, and its mate will quickly rise with it ; the next pair of leaf- lets soon fold together in a similar manner, and so on with succeeding pairs, until all of the leaflets of a secondary petiole have responded to the stimulus received by the upper leaflet ; indeed, all of the leaflets on all of the sec- ondary petioles may respond to a stimulus received by a single leaflet. There is, therefore, a transmission of a stimulus from one part of the plant body to another, such as takes place in animals by means of the nerves ; but FIG. 62. -1,1 in plants there are no struc- A, mature leaf of the Sensitive Plant fully tures Corresponding to the expanded; B, the same after stimula- tion. After DUCHARTRE. nerves of animals, and the exact manner of the trans- mission of a stimulus is not positively known. It is known, however, that in the case of the sensitive plant the trans- mission can take place through portions of the petiole which have been killed. Whatever the method of trans- mission may be, the reception of the stimulus is by the living protoplast, and the reactions which follow are caused by it. The benefits to be derived from actions of this kind are obvious : in rain or hail storms, or in strong winds, the leaflets fold together, and become much less liable to injury. Mimosa pudica affords an example of extreme sensitiveness. There are many other sensitive plants belonging to the same family which are of common occurrence; Cassia chamcecrista and nictitans and Schrankia uncinata are good examples. Growth and Movement. 127 FIG. 63. Dion&a muscipula. Some of the leaves stand open, and others are closed after stimulation by contact with insects. After KERNER. 98. Action of Venus's Flytrap. In Venus's flytrap, Dio- ncea muscipula (Fig. 63), and in sundew, Drosera rotnndi- folia (Fig. 65), we find still more wonderful sensibility and transmissions of stimuli. The two halves of a leaf of Venus's flytrap are capable of closing together as if they were hinged along the median line (see Fig. 64). The margin of each half is provided with from 12 to 20 teeth, and at the center of each half there are three hairs and numerous rose- colored glands. The three central hairs are specially con- cerned with the reception of stimuli, for although the leaves are impassive to contact at other places, when any of the hairs have been touched, the two halves close up rapidly until the marginal teeth are interlocked. The hairs are sensitive in this way to solid bodies, but not to the wind and rain. When an insect has been caught by the closing leaves, the glands on each half pour FIG. 64. M, leaf of Dioncea muscipula; N, cross section of the trap part of the leaf in its closed position. After KERNER. out a digestive ferment, and the insect is held until it is digested and absorbed, this process requiring from one to two weeks, according to the size of the insect. Then 128 Introduction to Botany. the leaf slowly opens and is ready for another victim. However, if the insect digested is large, the leaf may find itself unable to perform its trap function a second time. 99. Behavior of Sundew. The leaves of Drosera, or sundew, are orbicular, and bear on their upper surface glandular structures resembling tentacles (see Fig. 65), the tips of which exude a clear viscous fluid. When an insect alights on the leaf it becomes entangled in the viscid ex- cretion, its struggles excite the glands to greater activity, and more and more fluid is exuded ; at the same time the tentacles bend down over the insect, and ren- der escape more difficult. The viscous fluid has the nature of a digestive fer- ment, and by it the insect is ren- dered soluble, andinthiscondi- ition is absorbed by the leaf. The glands appear insensible to falling raindrops, but Darwin found that motion was induced when he placed on a ten- tacle a bit of hair weighing only y^^- of a grain. He found the tentacle to be quite sensitive also to very dilute solutions of nitrogenous salts ; they bent downward com- pletely when the leaves were immersed in a solution of ammonium carbonate so dilute that each gland could absorb no more than 37 oFo wo of a grain. This experi- ment serves at least to show that the sensibility of plants Leaves of Drosera rotundifolia, a, after stimulation by contact with an insect, and b, with all of the tentacles expanded. After KERNER. Growth and Movement. 129 may approximate or even surpass in some respects that of animals. 100. Spontaneous Movements. The movements of plants which have thus far been mentioned are evidently induced FIG. 66. Two photographs of the same seedling Morning Glory. A, after growing under usual conditions, the light stronger from the right ; B, after revolving on a uni- versal axis immediately following the condition shown in A. or guided by some external force, although in all cases the protoplast is the immediate cause of the movement. There is, however, another class of movements which seem to require no external stimulus other than those conditions which are necessary to the healthy existence of the plant. 130 Introduction to Botany. The growing apices of roots and shoots are almost con- stantly in motion, describing more or less irregular ellipses. Such movements are usually so slight as to be inappreci- able without the use of instruments for measuring move- ments through minute distances. 101. Twining Plants. The rotating movements of the apices of twining plants differ from spontaneous move- ments, not only in degree, but also in kind, for they depend on gravity for their accomplishment. This is shown by Fig. 66, which illustrates a morning-glory that has grown up a support under normal conditions, and the same plant after it has been revolving on a horizontal axis and on a vertical axis at the same time for a period of about eight hours. In the latter instance the plant not only ceased to twine, but actually untwined as far back as growth in length was still taking place. The revolution of a plant on both horizontal and vertical axes at the same time elimi- nates the directive influence of all exterior forces ; but that it is the elimination of the influence of gravity, and not that of light, which has caused the plant to untwine is shown by the fact that under otherwise normal conditions it continues to twine in darkness. 102. Method of Twining. Most twining plants twine contrary to the movement of the hands of a watch, that is, the coil facing the observer passes from the left below to the right above. Some plants, however, twine in the opposite direction, and some twine indifferently in both directions. The seedling twining plant does not show a tendency to twine for the first one or two internodes, but after that the apical portion bends over by its own weight to a position more or less horizontal, and then, if it is a left to right twiner and the apex is bent toward the north, for instance, the east side of the stem begins to grow faster Growth and Movement. 131 than the others, causing the apex to bend toward the west ; then the region of greatest growth is on the north side, resulting in the bending of the apex toward the south, and so on. By movements of this sort the plant is able to feel about in space for some support, and having found it to twine about it. If growth ceased in the coils as fast as they were made, the plant would rise upward little or not at all, and the successive coils of the stem would lie near together or over each other. This, however, is prevented by the continued growth of the stem for some time after the coils have been laid down, the growth then being most rapid on the under side of the coils, causing them to rise upward and become spread apart in the form of a spiral ; at the same time the stem is brought into closer contact with the support. The benefit of the twining habit is easy to see, for those plants which possess it are able to raise their leaves to the sunlight with a very small expenditure of energy and materials for the construction of strong stems. 103. Source of Internal Energy. How the living proto- plast is able to carry out the processes of growth and movement is a mystery. We know in regard to it, how- ever, that the protoplast ceases its activity and dies unless a certain amount of internal energy is available, resulting from the oxidation of the substance of the protoplast and of reserve materials ; no amount and no form of external energy can take the place of this. The more rapidly growth and movement take place the greater the amount of materials consumed. This oxidation of the substance of the protoplast and of the reserve materials is the essen- tial process of respiration, in plants as in animals. The active, or kinetic, energy resulting from respiration is in 132 Introduction to Botany. part immediately employed in the work of the protoplasts, and in part lost to the plant in the form of heat by radia- tion and conduction, and in the evaporation of water from the tissues. The internal energy which appears during respiration was obtained for the most part from the sun during the process of photosynthesis, and in part from the salts from the soil, and stored within the plant in the form of potential energy in starch, sugar, proteids, etc. ; and as active energy from the sun was required to form these sub- stances, so now it is evolved when they are broken down by oxidation. If we are to understand the essential thing about photosynthesis, we must perceive it as a process of storing the sun's energy in such a form as to make it available to plants by night as well as by day, and through- out all seasons of the year. 104. Oxidation a Vital Process. The process of respira- tion is not a passive oxidation, but is induced, and to a certain extent regulated, by the living protoplast. In plants, however, the regulation of oxidation is not by any means so exact as in warm-blooded animals, whose tem- perature is allowed to fluctuate only within very narrow limits, while the temperature of plants under normal con- ditions seldom differs much from that of the surrounding atmosphere. 105. Annuals, Biennials, and Perennials. A large class of plants bears seeds the first year, and in so doing these plants send into the seed so much of their stored energy that they are unable to survive the winter, or in some cases even to continue to the end of the summer. Such pi? its are known as annuals. Many other plants store up the energy accumulated by photosynthesis in underground parts, such as tubers, bulbs, etc., and having survived the winter produce their seeds and die at the end of the second Growth and Movement. 133 season; these are known as biennials. Still other plants keep in reserve sufficient energy to maintain their indi- vidual existence year after year ; these are termed peren- nials. The production of seeds is in the interest of the species, but not of the individual, upon which it is a severe tax, and only those plants can survive it that can retain within their own bodies a good amount of reserve energy. Some perennials further protect the individual life by alternate years of seed-bearing and sterility. 106. Length of Life. Some perennials attain an enor- mous age. A Taxus tree in Kent is considered to be 3000 years old, and an Adansonia in the Cape Verde Islands and a Taxodium in Mexico appear to have lived for 6000 years. It must be remembered, however, about plants of great age, that those of their tissues which are actually alive are of comparatively recent production ; the older tissues are gradually dying, while new tissues are being formed. Since perennial plants are annually rejuvenated by the formation of new tissues, it would seem that they might live indefinitely; but changes in the character of the soil, the ravages of storms and parasites, and com- petition with other individuals sooner or later bring their life to an end. 107. Nature of Growth. If we were to attempt a formal definition of growth, we might say that it is any permanent change in the form and size and internal structure which is brought about by the action of the protoplasts. Growth does not always involve an increase in weight, for germi- n ting seeds are actually decreasing in weight by the oxida- tk i of their reserve materials ; neither could temporary incr ^ase in size by the imbibition of water be classed as growth. CHAPTER VII. MODIFIED PARTS. PROVIDING MATERIALS. Material for the study of the morphology of spines can be procured at any time of the year, but branches for the study of the spines of bar- berry should be gathered while' in leaf, and either pressed or preserved in 2 % formalin. The wild smilax, whose tendrils are excellent material for morphological study, should be gathered during the summer and preserved as suggested for barberry. The greenhouse smilax can, of course, be obtained at any time of the year from greenhouses ; and nothing could be better than this for testing the ability of students in seeking out morphological evidence. Utricularia should be gathered from ponds and shallow lakes during the summer and preserved in 2 % formalin. OBSERVATIONS. Most plant members are either roots, stems, or leaves, and for the sake of classification these may be taken as the morphological elements, although some structures have a different origin. To determine the origin of a modified structure, that is, whether it is a root, stem, leaf, etc., evidence along the following lines should be sought : (i) arrangement; (2) relation to other structures; (3) tran- sitional forms; (4) construction. Thus, under i, is there a definite arrangement, a fixed angular divergence ? Under 2, does the structure have a definite and constant relation to a leaf or bud? Under 3, can forms be found which are less and less like the modified form in question, and more and more like a typical morphological element ? Under 4, 134 Modified Parts. 135 is it composed of bark, wood, and pith, or of one or two of these ? The evidence under 4 is not entirely reliable, since the modification of a structure may involve the suppression of some of its tissues. Before proceeding with the study of modified structures, write out the characteristics under I, 2, and 3, of a typical root, stem, and leaf (see Discussion no). It must be remembered that form and physiological function do not furnish reliable evidence as to the mor- phology of a modified structure ; this should be tested as you proceed with the studies outlined in this chapter. 109. Make a drawing of a spine of wild plum, showing its form, size, mode of attachment to the stem, and position on the stem with reference to nodes and internodes. Show its relation to buds, branches, leaves, or leaf scars. To show the attachment to the stem, make a median longitu- dinal section through the spine and the branch which bears it, and draw the cut surface. no. Give the morphology of the spine, that is, state what one of the morphological elements has been modified to form this structure, and give in your notes all of the evidence for your decision, as suggested under I, 2, 3, etc., of the introductory note. Refer to the details of your drawings by letters or numbers for each point of evidence. Determine the probable function of the spine, and give reasons in full for your conclusion. It is not possible to demonstrate a useful function for every structure. Some modified structures seem to have arisen either from lack of nutrition or from abundant nutrition, and in either case they may, or may not, be useful. The student should not attribute a function to a structure without good evidence. in. In a similar manner, work out the morphology of the spines of the honey locust, black locust, prickly ash, and osage orange. 136 Introduction to Botany. 112. Determine, as above, the morphology of the ten- drils of the wild smilax and Virginia creeper, or grape. 113. Work out the evidence for the morphology of the spines of barberry. 114. Determine the morphology of all structures which are borne on the stems of Asparagus medioloides (green- house smilax). 115. What is the morphology of the prickles of rose and gooseberry ? 116. Determine the morphology of an onion bulb. 117. What is the morphology of the tuber of Irish potato, and of the structures borne on it ? 1 1 8. Determine the morphology of the bladders of Utricularia or bladderwort. DISCUSSION. 108. Diversity of Plant Forms. The great diversity of plant forms, as we now find them, has doubtless been evolved from comparatively few and simple forms. No two plants are entirely alike, and probably no structure is exactly like any other of the same kind. Compare the leaves on a plant and note how dissimilar they are in form, size, and outline, and what endless varieties of leaves are on the different kinds of plants. Such facts as these are an expression of the extreme plasticity of the plant body, which seems to respond to external conditions and forces, and to internal tendencies, like clay to the hands of the potter ; yet we must remember that the infinite variety of forms which we now see has been evolving through the untold years since life began upon the earth. 109. Morphological Elements. After plants had ad- vanced in their evolution from the un differentiated body known as the thallus (see pages 257 to 285) to the forms Modified Parts. 137 having roots, stems, and leaves, they seem to have found in these a sufficient number and kind of members for the suc- cessful nutrition of the individual (we may consider struc- tures of the nature of hairs and prickles as outgrowths of roots, stems, and leaves without grouping them as distinct morphological elements). We find very few plant members which may not be classified certainly as either roots, stems, or leaves, and for this reason we may speak of these members as the morphological elements, without im- plying that no other members may sometimes occur. Thus, when for any reason plants have need of new structures, it is their habit to modify one of these elements to meet the new demand. When Solanum jas- minoides, for instance (Fig. 67), was acquiring the climbing habit it put into its petioles sensibility to contact, and power to respond in such a way as to twine about the object with which it came in contact. Or, when the turnip began to store up food for use in the succeeding year, in- stead of producing a new member as a storehouse for reserve food, its tap root was incited to increase in size sufficiently for this purpose. So, too, when buds were to be protected, internodes were kept short, and the leaves were so modified as to enwrap the tender parts in the form of tough resistant scales. Ex- amples of this kind might be cited at great length. In acting in this way, plants have shown themselves to be wise economists, for it is certainly moving along lines of FIG. 67. Shoot of Solanum jasminoi- des, showing the leaf peti- oles acting as tendrils. After GRAY. 138 Introduction to Botany. least resistance to modify old members rather than to pro- duce entirely new ones. 110. Characteristics of Morphological Elements. Since there is such diversity in form as well as in function of roots, stems, and - leaves, how are we to tell when we are dealing with these members ? By a comparative study, we find that there are certain characters which appear so fun- damental as to furnish reliable evidence for recognizing the members to which they belong. Thus, roots are out- growths from stems or from other roots, arid do not, as a rule, arise in definite order or definite angular divergence, except in the case of the secondary roots of seedlings ; and although they may bear adventitious buds, they do not directly bear leaves. Stems directly bear roots, leaves, and buds ; and most lateral stems arise either in, or just above, the axils of leaves. Leaves are borne directly on stems ; they have a definite angular divergence, and they commonly bear buds in their axils. Mere outgrowths of the epidermis, or bark, such as hairs and prickles, differ structurally from the morphological elements in containing none of the parts of a vascular bundle, such as wood fibers and tracheal tubes. Whatever form, size, structure, color, or function a member may have, if it possess a set of characteristics as above stated we may classify it accordingly. 111. Modified Roots. Roots are very commonly modi- fied to serve as storehouses for nourishment ; in such cases they consist for the most part of thin-walled tissues, to and from which the reserve materials can readily pass in solu- tion. The dahlia and sweet potato afford familiar exam- ples of roots of this kind. In our western plains, Ipomcea leptophylla has a storage root weighing from 10 to 100 pounds. The climbing roots of the trumpet creeper occur in clusters at the nodes, while those of the poison ivy occur Modified Parts. 139 FIG. 68. Artichoke tuber. After GRAY. in two almost continuous rows (see Fig. 17). In these cases, the real nature of the roots is not much masked. The aerial roots of orchids and the parasitic roots of Cuscuta, although modified for absorption under special conditions, have still retained much of the appearance of typical roots. The supporting roots of the banyan, however, extending to the ground, have the general appearance of stems, but their identity is easily determined by the method and place of their ori- gin on the branches. 112. Modified Stems. Stems are frequently modified to grow beneath the surface, and there attain considerable size for the purpose of storage ; the potato and artichoke are good ex- amples. Al- though grow- ing beneath the ground like roots, and FIG. 69. Nelumbo lutea. v, a tuber which has survived the winter; x and w, horizontal offshoots growing beneath the mud, serv- ing the purpose of multiplication ; y, shoot growing deeper preparatory to the thickening of some of its internodes for the purpose of storage, as in v. The horizontal lines be- neath the leaves indicate the surface of the water. 140 Introduction to Botany. having a function quite different from that of typical stems, their morphological nature is made clear by their much reduced scale leaves, in the axils of which buds occur (see Fig. 68). Such modified stems also have a reproduc- tive function, since, after they have survived the winter, their buds develop into new shoots. Stems which are modified for the purpose of multiplication are illustrated by the above-ground runners of the strawberry and the underground runners of the goldenrod. The yellow water lily, Nelumbo lutea, affords an example of a stem which is at first slender, and runs along in the mud beneath the water for the purpose of multiplication, and later becomes much enlarged in certain of its internodes for the purpose of storage (see Fig. 69). The leaflike structures of Ruscus are really stems, as is shown by the fact that they do not bear buds in their axils, but are themselves borne in the axils of scales which have a regular angle of divergence on the main stem ; the scales being, therefore, morphologically, leaves, and the leaflike structures, stems. But we have still further evi- dence, for the leaflike structures, termed cladophylls, bear flowers in the axils of scales that are evidently leaves (see Fig. 70). To sum up the evidence: The cladophyll is borne in the axil of a leaf, and itself bears a leaf and flowers. The evidence is, therefore, strong that it is a stem. The fact that it looks like a leaf and performs the photosynthetical function of a leaf should not be taken as evidence that it is not a stem, for we have already seen that the forms of plant members can vary indefinitely, and that they may be put to a variety of uses. The green, thick stems of cacti perform the double function of storage and photosynthesis, while the leaves have become reduced to spines that have entirely lost their normal function of photosynthesis. Modified Parts. 141 We can only conjecture how such modifications of form and changes of function have come about. In the case of cacti, we can see that the reduction of the leaves and the thickening of the stems have fitted them to in- habit desert regions by a reduction of the tran- spiring surface, and an increase of the water- storage tissues, of which the bulk of the plant con- sists. In the case of Ruscus, it may be that some time back in its ancestry it became de- sirable to reduce tran- spiration on account of scarcity of water, or in- ability to absorb the water because of its saltiness, or because of the low temperature of the soil (see the Chapter on Ad- aptation to environment); under which conditions the plants with the smallest leaves might have fared the best and produced the greatest num- ber of offspring. Then it might have come about in the course of time that the species was represented by indi- viduals whose leaves were mere scales. Later, the condi- tions might have changed so that water could be more readily obtained ; it would then have been desirable to increase surfaces for photosynthesis, but the scale leaves, being poorly nourished and reduced members, would have FIG. 70. Shoot of Ruscus hypoglossum, showing leaf- like stems or cladophylls. After K.ERNER. 142 ' Introduction to Botany. been unable to produce variations from which a selection of suitable forms could be made. The better-nourished stems, however, would have been able to do this, and finally the forms which we now see could have been evolved. This description is of course conjectural, and may, or may not, approximate the true events. 113. Modified Leaves. Leaves modified for storage are found in the scales of the bulbs of onion, in the thicker scales of tiger lily bulbs, and in the leaves constituting the cabbage head. The fleshy leaves of Agave Americana are storehouses of water and reserve food, while at the same time they carry on the normal constructive functions of ordinary leaves. The thick leaves of succulent plants, such as Mesembryanthemum and Sedum, serve as store- houses for water. Leaves which have been modified to serve a protective function are seen in bud scales, and in the spines of cacti, and in barberry. Parts of leaves which have been modified to form tendrils for climbing, we find in Solatium jasminoides, the garden pea, etc. We have already, in the last chapter, become acquainted with leaves which have motor organs, digestive glands, sensitive hairs, etc., for the capture of insects. There are other modified forms of leaves which entrap insects and apparently use them for food. These are the pitchers of the pitcher plants and allied forms, and the bladderlike traps of the bladderwort. In these cases, the modifications are so great and their adaptation as traps is so wonderful that they deserve a somewhat detailed description. 114. Pitcher Plants. The pitcher plants (Nepenthes) are natives of the old world tropics. The pitcher is borne at the end of a slender prolongation of the petiole, and is probably itself a part of the petiole which has grown out in the enlarged tubular or pitcher form. At the top of the Modified Parts. pitcher is a lid (see Fig. 71), which may correspond to the blade of the leaf. The lid, in the mature pitchers, stands open, and may serve as an attraction for insects. The border of the mouth of the pitcher is rolled inward and downward, and often there are stout teeth extending downward on the inner edge of this border. Honey glands occur on the out- side of the pitcher, on the in- rolled border, and on the inner surface of the lid; by this means insects which alight on any por- tion of the pitcher are lured to the edge of the open mouth. Once over the border, the insect slips into the pitcher, which con- tains a fluid having digestive properties, and so the insect be- comes digested and absorbed. The pitcher plant called Dar- lingtonia shows a still greater degree of modification. In this plant the top of the pitcher arches over so that the mouth is directed downward (see Fig. 72), while extending beyond the border of the opening is a bi- parted, brightly tinted expansion somewhat in the form of a pennant, which no doubt acts as an attraction to insects. The arched dome, or helmet, at the top of the pitcher is marked with red, and studded over with spots desti- tute of color, so that the light can shine through them as through a window. Nectar glands on the outer surface of FIG. 71. Nepenthes villosa. After KERNER. 144 Introduction to Botany. the pitcher and under surface of the pennant lure both creeping and flying insects to the mouth of the pitcher, and after they have passed beyond the incurved border, which they are likely to do, they meet with a smooth surface to which it is impossible for them to cling, and are precipi- tated to the bottom of the pitcher, where a di- gestive secretion awaits them. The attempts of creeping insects to crawl out of the pitchers are frustrated by stiff, downward-pointing hairs. Winged insects can fly upward, but instead of finding the open- ing they are attracted by the transparent spots in the over- arching helmet, against which they vainly beat until they be- come exhausted and fall to the bottom, where they become im- mersed in the digestive fluid. The pitcher plant known as Sarracenia variolaris, which is common in the southern states, although not so elaborate, has essentially the same devices as Darlingtonia, for alluring and entrapping in- sects. Investigations thus far leave us in doubt whether the main function of these pitchers is the capture of insects for the food of the plant, or whether they are primarily water reservoirs to hold water that has been exuded from the plant itself, or caught from the rain in those cases FIG. 72. Darlingtonia Californica. GEDDES. After Modified Parts. where the pitchers stand open. Insect-catching, at any rate, appears to be one of their important functions. It is not easy to conceive how the modifications into pitchers have come about. We know that there is in plants a capacity to vary which is apparently stimulated to activity by both internal and external causes. Useful variations would be likely to persist and become more pronounced by the produc- tion of more numerous and stronger offspring, of which those having the most useful varia- tions would finally predominate, because bet- ter fitted to contend for soil, air, and sunlight. But how, in this case, the variation became started along the line of pitcher formation lead- ing finally to the win- dowed dome, slip- pery surfaces, and detaining down- ward-pointing hairs can only be an- swered with conjec- tures. 115.Bladderworts. - Not less wonder- ful are the modified leaves of the common Utricularia or bladderwort. This is an immersed, floating water plant (see Fig. 73, A). Some of its leaves are much divided and threadlike, and others are modified in the form of little bladderlike traps adapted to catching very minute water animals. The en- trance into the cavity of the bladder is provided with a door which swings inward, but never outward, because its FIG. 73 . Utricularia grafiana. A, showing flower rising above the water, and below the water finely divided foliage leaves, and bladderlike leaves. After KERNER. B, longitudinal diagram of a bladder leaf of Utricu- laria vulgaris, showing trap door opening inwards. 146 Introduction to Botany. free edge swings against, and overlaps on the inside, the thickened lower border of the opening (see Fig. 73, B}. Stiff hairs fringe the opening on the outside, and probably offer a place of refuge for small water crustaceans and various small larvae when pursued by larger animals. The little animals are apt to push their way farther into the bladder, the door of which easily rises to admit them, but never swings outward to permit their escape. Finally they die, become disintegrated by bacteria inhabiting the in- terior of the bladders, and the soluble products of their decomposition are absorbed by the inner surface of the bladder, and thence distributed to the rest of the plant. Experiments seem to show that the animal food thus ob- tained is useful in the nutrition of the bladderwort. CHAPTER VIII. FLOWERS. PROVIDING MATERIALS. If the work in botany is begun soon after the Christmas holidays, the early wild flowers will probably begin to appear by the time the work already outlined has been completed. When there is doubt of the availability of wild flowers at the required time, material placed in formalin the previous summer should be at hand ; or arrangements should be made with a greenhouse for forms which can be supplied in abundance, such as sweet alyssum, Chinese primroses, Freesias, Tri- teleias, and single hyacinths. It is desirable to select for preservation in formalin flowers which are somewhat stiff and leathery, such as those of the honeysuckle, trumpet creeper, Yucca, tiger lily, and some of the larger composites. The Yucca is particularly good for introducing the student to the structure of flowers, since all of its parts are large and simple in construction, and it has the further advantage of being one of the most interesting flowers in the method of its cross pollination. (See page 196.) As soon as the structure of a few typical flowers has been learned, wherever practicable, entire plants should be provided for the study of plants as a whole. When flowers have become sufficiently abundant out of doors to admit of choice, only those forms should be selected which show well some definite facts of floral structure, adaptation to pollination, or relation- ships such as are exhibited by the different species of a genus. No- where in an introductory course in botany is the limited time usually available more in danger of being misapplied than in the promiscuous study of flowers without reference to some definite problem. To illustrate : Anemone or Ranunculus might be chosen to show a simple type of flower, with parts distinct and regular ; larkspur, to bring out relationship to the simple Anemone type, but with profound modi- 147 148 Introduction to Botany. fications to insure cross pollination (flowers of different ages are necessary to show all that this flower has to teach) ; Oxalis, to show special devices for cross pollination, each student being supplied with the two forms of Oxalis violacea, for instance, which may be found growing together in the same patch ; all obtainable species of violets, to exhibit special devices for cross pollination, and considerable varia- tions in the foliage and habits of plants having flowers of essentially identical structure. This comparative study of violets is excellent in showing how the flower, more than any other structure, gives the most reliable clews to plant relationships. It is best to have the whole class at one time working on the same kind of flower, in order that the discussions and blackboard demonstra- tions, which are frequently desirable, may be founded on the experience of all of the students. The material should therefore be chosen in time to have an abundance provided for each day's work. OBSERVATIONS. 119. Make a drawing of the flower, showing its position on the branch and its relation to outgrowths from the branch (a, Fig. 74). 1 20. Dissect the flower into its separate parts, and make sketches showing the form of each ( -^ Vat'Aveo^lem ;elteru ES^ .Mu^:. _. >; .,._.. il| XIV > .Nffl FIG. 90. Reduced facsimile of the title-page of Sprengel's book, " The Discovered Secret of Nature in the Structure and Fertilization of Flowers." from afar as receptacles of nectar by insects which are fly- ing about in quest of food. Flowers. 175 "While in the summer of 1787 I was studying some species of Iris I soon found . . . that the nectar is fully protected from the rain, and that there are specially colored places which lead the insects to the nectar. But I found still more, namely, that the flowers cannot possibly be fertilized in any other way than by means of insects, and in fact by insects of considerable size. . . . My in- vestigations ever more and more convinced me that many, indeed perhaps all, flowers which have nectar are fertilized by the insects which obtain food from this nectar." Figure 90 is a reduced facsimile of the title-page of Sprengel's book; the various flowers of the border -give some idea of the variety of forms worked out by him. 126. Devices for Cross Fertilization. The ability of plants to adapt their members, by modifications of form and structure, to various conditions and ends, is perhaps best shown in the construction and behavior of their flowers. The end which most flowers seek to attain, as long since pointed out by Sprengel, is cross fertilization, and the agents to which they have to adapt themselves are wind, insects and other animals, and water. In order that cross fertilization may be achieved it is of paramount importance that self fertilization should be prevented, and we accord ingly find special devices having this end in view. The chief of these devices are as follows : (i) Only one sex is represented in each flower, but both sexes occur on the same plant. The flowers which contains the stamens are called staminate, while those which contain the pistils are called pistillate ; the flowers in this case are called monoecious (see Glossary for derivation of terms). (2) The pistillate flowers only are borne on one plant, while the staminate flowers are borne on another plant ; such flowers are called di&cious. (3) The flowers contain both sexes, 176 Introduction to Botany. but (a) the pistils and anthers are not mature at the same time. Thus the stigmas may be ready to receive the pollen, but the anthers are not ready to break open and discharge the pollen, or vice versa ; such flowers are called dichogamous. If the stamens mature first, the flowers are proterandrous ; if the pistils mature first, they are proterogynous. (b) The stamens and pistils may differ greatly in length, so that the pollen would not be apt to at- tain to the stigmas of the same flower. Flowers of this kind are called dimorphic if the stamens and pistils are each of two different lengths, or trimorphic if of three different lengths, (c) The relative posi- tion of stamens and pistils may in other ways be such as to keep the pollen from the stigma, or other parts of the flower may intervene between them. The devices to prevent self fertilization are also in the interest of cross fertilization. If the flowers are dioecious, insects in going from one plant to another are quite certain to carry pollen from the staminate flowers to the stigmas of the pistillate, or the wind may accomplish the same thing. An insect in visiting dichogamous flowers would, in the case of proterandry, carry pollen from the stamens of FIG. 91. Cross pollination of Primula, a di- morphic flower. In A a bee is gathering nectar at the base of the pistil while its head is in contact with the anthers inserted in the throat of the corolla. In gathering nectar from the long-styled flower, B, the pollen on its head will be deposited on the stigma, and at the same time pollen from the low stamens will be brushed off on its proboscis at the right height to be transferred to the stigma of a short- styled flower as in A. WISE. Flowers. 177 the younger flowers to the stigmas of the older, or vice versa in case of proterogyny. In dimorphic flowers the pollen from short anthers would quite certainly be deposited by insects on the stigmas of the short pistils, as in going from B to A, Fig. 91. Adaptations for cross fertilization are perhaps best seen in the various adjustments of flowers to the agents which are to transport the pollen and deposit it on the stigma. These agents, as has been stated, are wind, in- sects and other ani- mals, and water. 127. Adaptation to Wind. Those flow- ers which depend upon the wind for transporting the pol- len are characterized by protruding stamens and a relatively large expanse of stigmatic surface ; this is well shown by Indian corn, whose staminate flowers surmount the plant and send forth numerous pendent stamens which offer their pollen to the wind. The long silken styles which protrude beyond the husks of the pistillate inflorescence, or ear, present a large surface for arresting the pollen as it is being carried about by winds. The pines, poplars, and willows illustrate the same thing in somewhat different ways. The pollen of the pine is borne in great abundance in the staminate catkins (see Fig. 92), and each grain is provided with two balloon-like expansions containing air, which contribute to its lightness FIG. 92. Staminate catkin of the Pine. 178 Introduction to Botany. and sailing qualities. The pistillate inflorescence is in the form of a cone (Fig. 93, a) whose scales are broadly expanded and collect the pollen as it settles down upon them, directing it downward to their axils, where it comes in close proximity to the micropyles of the naked ovules (see Fig. 94). The staminate catkins of the poplars are shaken and emptied by the wind, while the branched and widely spreading stigmas of the pistillate flowers, occurring on a different tree, catch and hold the pollen which is wafted to them. It is characteristic of flowers which depend on the wind that they are either monoecious or dioecious. It is plain that this mode of pollen transference is ex- FIG. 93. Pistillate inflorescence of the pine. At a, young cone of the current spring ready to receive pollen ;, cone which the pre- pensive, SHICC ITiOSt of the vious spring was like a; c, cone one year older than b ; here the scales have pollen must be lost in tran- spread apart and the seeds have dropped out. sit. There is some com- pensation, however, in the fact that allurements for insects in the form of brightly colored corollas, nectar, and fragrant odors are not neces- sary, and are accordingly not produced. 128. Cross Pollination by Water. In the case of flower- ing plants which are entirely submerged in water, the pollen frequently has the same specific gravity as the water, and Flowers. 179 FIG. 94 . boat-shaped Fruiting Scale or Carpel from a young Pine Cone. A, seen from the front, showing two ovules; B, diagram of a longitudinal section of A, seen from the side. m, micropyle ; n, embryo sac. A, after BESSEY ; B, after CALD- WELL. is readily dispersed from flower to flower at any depth. In the case of Vallisneria spiralis (see Figs. 95-96) the pistillate flowers rise to the surface on slender stems. The staminate flowers, which are formed under the water, break loose from their stems and float on the surface, the calyx consisting of sepals which buoy the stamens above the surface, and allow them to float high and dry. The sta- mens bend outward beyond the rim of the calyx, and when the stami- nate and pistillate flowers are brought together by the wind or currents of water, the anthers come in contact with the stigmas and effect their pollination. The stem which bears the pistillate flowers then coils itself spi- rally and draws the flower to the bottom of the water, where the seeds may ma- ture undisturbed. 129. Adaptations to In- sects. The most wonder- FIG. 95. f ul modifications of flowers Vallisneria spiralis. The plant on the left are found in those f OrniS bears staminate flowers which are break- ing away and rising to the surface. The which are adapted to CrOSS plant on the right bears a pistillate flower pollination by means of in- rising on a long stem to the surface. After KEENER. sects. These have had to i8o Introduction to Botany. provide for the allurement of insects by offering them nectar and pollen for food, and for attracting their attention by means of odors and bright colors ; and at the same time they have had so to con- struct and arrange their parts that in- sects in securing food would necessarily carry the pollen from one flower to the stigma of another. 130. Allurement by Pollen. Some flowers secrete no FIG. 96. Pistillate and staminate flowers of Vallisneria spiralis. On the right a staminate flower has floated against nectar but offer an the pistillate flower and an anther is touching one abundance of pollen, of the stigmas. After KERNER. Roses, Anemones, and poppies are of this sort. Flowers of this kind are more or less erect so that the pollen may not fall out, and the stamens are usually numerous. Insects which feed on the pollen of such flowers are certain to get their bodies dusted over, and in this way they carry the pollen from flower to flower. 131. Allurement by Nectar. Nectar is the most com- mon and most important allurement for insects. It is a more or less watery solution of sugar, and of certain salts and aromatic substances, secreted by a special tissue known as the nectary, and expelled at the surface by transfusion through the epidermis, by breaking down of the tissues, or through a special opening of the nature of a stoma. The nectar either remains clinging to the surface of the nectary or it gathers in large drops and falls into a nectar recepta- cle provided for it, as in the case of -violets, where horn- Flowers. 181 like outgrowths from the two lower stamens secrete the nectar and pour it into a cup formed by the base of the lower petal. The nectaries may occur on any part of the flower, but they are most frequently found at the bases of the stamens, petals, and ovaries, and rarely on the calyx. In the plum and peach they form a thick inner lining of the cup-shaped receptacle. In Nasturtiums the nectar is secreted in a long spur from the calyx. Some flowers of simple construction expose their nectar freely to all sorts of insects, but others conceal it in various ways so that it is accessible only to insects of certain kinds. A frequent device is to have some parts of the corolla close over the way to the nectar so that small insects which would not assist in cross pollination are excluded, and only those which are strong enough to push aside the barrier or have proboscides of proper construction to thrust past it can obtain the nectar and accomplish the transference of the pollen. The student is quite certain to find that irregularities and complexities of floral structure are in the interest of the protection of the nectar or pollen and the transference of the latter from one flower to another. 132. Color and Fragrance. As Sprengel pointed out, flowers not only provide food for insects, but they also furnish advertisements in the way of brilliant colors and agreeable odors to notify insects from afar where food awaits them, and lines, spots, etc., of special color to show insects coming to the flowers the direct way to the nectar. It appears from various experiments that the odor is most effective in attracting insects from a considerable distance, and that on the nearer approach of the insect the color be- comes an important guide. There seems to be no doubt 182 Introduction to Botany. that insects have a keener sense of smell than our own, and are attracted by the odors of flowers which we cannot detect; but their vision, except at short distances, is not sharp. They, however, appear to appreciate differences in color at a distance where the forms of objects are still indistinct to them. 133. Sense of Smell in Insects. The nerves of insects that are sensitive to odors ramify and come to the surface in the antennae, which are under- stood to be their organs of smell (Fig. 97). That the sense of smell may be very keen in in- sects is shown by the fact that they can go unerringly Photomicrograph of the head of a Sphinx Moth, X 3, showing the antennae in which are located the nerves to mCOnSplCUOUS of smell, and the large compound eye. The long pro- and Concealed boscis is coiled like a watch spring out of sight be- ., neath the eye. flowers which to US may be scentless. 134. Sense of Sight in Insects. The eyes of insects are compound, that is, they are composed of numerous smaller eyes all grown together, and in communication with the same optic nerve, and therefore really constituting one organ The number of single eyes or facets may amount to twenty-five thousand. The end of each facet has the appearance of a convex hexagonal disk. Figure 98 repre- sents a longitudinal section of the eye of a cockroach which may be taken as a type of the compound eye. At / is a lens-like body, clear as glass, whose outer face is at the surface of the eye. The light passing through this FIG. 97. Flowers. 183 next traverses the crystal cone k y which is also a trans- parent lens. The nerve tissue /, m, and ;/, is in immediate communication with these lenses, and transmits the light stimuli to the main optic nerve, and thence to the nerve ganglia which represent the brain. The compound eye of an insect does not form an image in the same manner as does the human eye, in which divergent rays of light from any point are brought to a focus on the retina, and a relatively bright inverted image is formed. Insects can, therefore, not see as well as we can. This appears to be borne out by the action of insects, which do not seem to appreciate the forms of objects well until they are quite near to them. FIG98 Since the main object of insects' Diagram of the compound Eye of an Insect. A, a surface view of some of the simple eyes united to form a com- pound eye. B, a longitu- dinal diagram of three simple eyes. See text. The image formed is said to be a mosaic, each simple eye contributing a distinct por- tion. After LUBBOCK. visiting flowers is that of obtaining food for themselves or their young, their relations to flowers will be better appreciated when the con- struction of their food-gathering ap- paratus is understood; and for this purpose the bees and butterflies will be chosen for examples, because they represent two kinds of insects which are most important to flowers. 135. Relation of Butterflies to Flowers. Butterflies sip the nectar only, and do not make use of the pollen ; al- though in getting the nectar they incidentally transfer pollen from flower to flower. They do not carry away 184 Introduction to Botany. and store nectar for themselves or their young, but take only what they immediately desire for food. They do not, on the whole, seem to require much food in the imago or butterfly state (the student will remember that in the first stage of their existence after hatching from the egg they are caterpillars), al- though they are sometimes so eager for the nectar that they may be caught in the hand while obtaining it. The organ by means of which the nectar is secured is known as the proboscis ; it is long and slender, and contains muscles, nerves, and air tubes, and a cavity for sucking up liquids (Fig. 99, A and B). When the proboscis is not in use, it is tightly coiled like a watch spring, and tucked away in A, longitudinal diagram of the head of a Butterfly, o, s, p, g, muscles operating small space beneath the ^ST5^"S: head ( cora P are Fi s s - 97 cavity ; t, oesophagus ; B, cross diagram and 104). The proboscis of butterfly's proboscis. The central n i-i j i cavity is for suction and the lateral cavi- 1S vei 7 flexible and IS ad- ties carry muscles, nerves, and air tubes, mir ably Constructed for After BURGESS. i r 11- probing for concealed nec- tar or for reaching to the bottom of flowers with long tubes, such as those of the morning glory, petunia, etc. Flowers which are especially adapted to butterflies and moths (the difference between butterflies and moths being inconsequen- tial) are so constructed that the proboscis comes in contact Flowers. i8 5 with both anthers and stigmas, so that the pollen is quite certain to be transferred from one flower to the stigmas of another. 136. Relation of Bees to Flowers. Bees gather and store up both nectar and pollen for themselves and their young, and are more indefatigable than all other insects in their visits to flowers. Their mouth parts are so constructed that they can transfer pellets of pollen, by means of their mandibles, directly to the so-called mouth or opening into the pharynx, whence it passes through the oesophagus into the stomach ; or they can adjust an elongated suction apparatus to the mouth opening, and by means of it suck up nectar from more or less concealed nectaries. % Since bees depend almost entirely The head and mouth parts of upon flowers for their food, and are at the same time of inestimable value to plants in accomplishing cross pollination, it may be taken for granted that the structures of bees, and of flowers visited by them, have been evolved side by side, and have influenced each other by their inter- dependence. The mouth parts of the bee (Fig. 100) are used, not only for collecting food, but also in the construc- tion of the comb, and in other manifold duties pertaining to the care of the young. The bee flies from flower to flower until the honey stomach (see Fig. 101) is extended to about T 3 g of an inch in length and T 2 g- of an inch in breadth ; it then flies to the hive, ble ; g , flap over the mouth ; ntx, maxilla; //, labial pal- pus; /, tongue or ligula with button-like extremity b. After CHESHIRE. i86 Introduction to Botany. and by a contraction of the honey stomach empties its load of honey into the cells of the comb ; then, urged by an irresistible instinct, it flies forth to repeat the process again and again until darkness sets in. It can be seen at once that the industry of the bee places it in the fore- front of insects useful in the cross pollination of flowers. FIG - I01 - As has been said, bees Longitudinal diagram of the head and a part a j so co H ect pollen as an of the body of the honey bee." g, the flap . r over the mouth opening; mx, maxilla; important food for them- //, labial palpi; /.the tongue; o, the oesoph- se l ves an( J t h e ir VOUng;. agus; s, honey stomach. When at rest + the maxillae, tongue, and labial palpi are Some pollen may be in- AffefcH a EtHi a R E indiCated by the dottedline ' cidentally swallowed with the nectar, but most of it is deftly transferred to the hind legs, where it is sometimes heaped up in large masses, having been rendered adhesive, if necessary, by being mixed with nectar. Figure 102 is a photo- micrograph of two legs of a honey bee, one loaded with pollen and the other empty. Some other bees, notably the green bees which fre- Photomicrograph of two posterior legs of Honey Bees, without pollen on the right, and with a load of pollen on the left, x 3. FIG. 102. quent the yellow pond lilies at early morning, Flowers. 187 have long curved hairs on the hind legs which serve as a sort of basket for the pollen, as shown in Fig. 103, a and b. Having now become somewhat acquainted with the equipment of butterflies and bees for dealing with flowers, it will be well to consider a few special cases showing how the need of the insect for food and of the flower for cross pollination are mutually satisfied. 137. Cross Pollina- tion of Datura. Many flowers possess long tubes at the bottom of which the nectar is stored ; such flowers usually have the way to the nectar obstructed by a constriction of the tube, or by out- FIG. 193. growths in the form of A < le s of a wild bee with hairs servin s as baskets 5 f for the collection of pollen ; B, the same laden hairs, etc., SO that Only w hh pollen. Photomicrograph X 4. those insects having long proboscides can reach it. The common jimson-weed (Datura stramonium) is an excellent illustration of this. The corolla is about five centimeters long, and the cavity of the tube is nearly closed at about the middle of its length by the insertion of the filaments there. When the flower opens in the evening, it emits a strong musky odor, and a large drop of nectar is already present in the bottom of the tube ; FO that large sphinx moths, leaving the places of seclusion occupied by them during the day, are attracted by the strong odor and white color of the flowers. Flying swiftly from flower to flower, the moth thrusts 1 88 Introduction to Botany. its long proboscis to the bottom of the tube and secures the nectar ; and while it is tarrying briefly at each flower, keeping itself poised by the swift vibration of its wings, it is pretty certain to touch with its proboscis both anthers and stigmas, which stand close together at about the same height near the mouth of the corolla. Both cross and self FIG. 104. Sphinx moth and flower of Datura stramonium, posed to show the relative lengths of the flower and of the moth's proboscis. Reduced rather more than one-half. pollination might be brought about in this way, but, as Darwin has shown, the foreign pollen would probably possess the greater potency, and cross fertilization would be apt to result. Figure 104 is a photograph of a sphinx moth and Datura flower, posed to show the relative lengths of the moth's proboscis and the corolla tube. 138. Cross Pollination of Sal via. In the Salvias, or sages, we find several contrivances working together for a common end. The corolla is tubular below and two- lipped above, the lower lip serving as an alighting place for bees, and the upper forming a protective covering for the stamens and style. There are two stamens of peculiar construction set one on either side of the mouth of the Flowers. 189 corolla (see Fig. 105). The filament (/) is very short and bears a two-armed connective (cc), the upper arm being long and thread-like and supporting a pollen-bearing anther, while the lower arm is short, spatulate, and sterile. By pressure on the lower arm the upper arm may be rotated FIG. 105. Pollination of Salvia glutinosa. i, a stamen. The upright column to the left of/ is the filament, c, c, the connective, anther bearing above and sterile below. 2 and 3, longitudinal diagrams of a young flower, showing the anther in its natural position in 2, and pushed down by a bee by pressing on the lower part of the connective, in 3. 4, a bee visiting a younger flower ; the anthers pushed down upon its back. 5, a bee visiting an older flower; the style having become elongated and pendent touches the bee's back. After K.ERNER. downward, the short filament acting as a fulcrum. When a bee which has alighted on the lower lip attempts to thrust its suction apparatus into the tube of the corolla, its head presses against the lower arm, and the two anthers are rocked forward until they press against the bee's body and discharge pollen upon it (3 and 4). In the younger flowers the styles remain close under the upper lip (dia- grams 2 and 3), but' as the flowers get older the styles bend down so that visiting bees would necessarily rub their backs against the stigmas (5). In this way the 190 Introduction to Botany. bees transfer pollen from the younger flowers to the stigmas of the older (4 and 5). 139. Cross Pollination of Or- chids. In orchids we find so'me of the most wonderful modifica- tions of the parts of the flower to secure cross pollination. Fig- ure 1 06 represents, in part, the construction of the flower of Catasetum tridentatum, a South American orchid. In this flower, as in orchids in general, there are three colored sepals and the same number of colored petals, one of the petals serving as a landing place for insects, and being prolonged into a spur be- low for the conservation of the nectar. The irregular central body c, known as the column, is A, longitudinal diagrams of the composed of the pistil Confluent flower of Catasetum tridentatum. ,! ,1 i T^, ,, the column; h, the sensitive Wlth the Sln g le Stamen. The spur; /, poiiinium; d, viscid disk, upper part of the column bears B, projection of the pollinium and , -,-, , f i i viscid disk after the stimulation tw P llen SaCS > ea ch of which of the spur by the touch of an contains a mass of pollen, /. insect. After K.ERNER. _,, ,, The pollen masses are con- nected by means of an elastic band with a body termed the viscid disk d, which is really a modified portion of the stigmatic part of the column. Running down from the central portion of the column are two slender horns, //, standing in the way of insects' which would gather the nectar or eat the fleshy parts of the flower/ As soon as an insect's head touches one of these horns, FIG. 106. Flowers. 191 a stimulus is transmitted to the column resulting in the sudden rupture of the tissues connecting the viscid disk with the rest of the column. The viscid disk is then jerked forward by means of the elastic band with sufficient force to pull the pollen masses, termed pollinia, from their pollen sacs and hurl them forward, disk foremost, to a distance of one or even three feet ; but if the insect is standing in the line of projection, which would probably be the case, the viscid disk is thrown against its head or thorax and sticks there. Thus the insect is made to carry away the pollen masses, which are sticking out forward as the insect enters the next flower. The flower just described is known as the male flower, that is, the pistil is abortive and does not bear seed. If the insect next visits a female flower, having a perfect pistil but abortive stamens, the pollinia will be thrust into a concave structure known as the stigmatic chamber, which has an adhesive surface capable of holding the pollinia with sufficient tenacity to wrest them from the insect. Then the pollen tubes grow into the ovary and cross fertili- zation of the eggs is accomplished. In this flower we see a marvelous correlation of modi- fied parts to attain a definite purpose ; but most wonderful of all is the sudden transmission of a stimulus due to the touch of the insect at one definite part of the flower, and a correspondingly sudden dissolution of. the tissues which hold the viscid disk in place. 140. Cross Pollination of Asclepias. In the genus Ascle- pias, we find an adaptation to cross pollination by insects scarcely less wonderful than that of the orchids. Asclepias cormtti (Fig. 107), common everywhere in this country, is perhaps the best species for demonstrating this. As shown in Fig. 108 the sepals (s) and petals (/) are reflexed; the Introduction to Botany. (r) are joined throughout their length, and are united to a thick and flat structure (t) at their apices, known as the stigmatic disk, which is also united with the top of the two pistils (n). The pistils are entirely inclosed by ^& -$$ the stamens an d the JB |^ Jf stigmatic disk. Five spreading, hollow re- ceptacles (v) for the nectar grow out and upward from the bases of the stamens. Each pollen sac con- tains a compact mass of pollen grains (w) which never become separated from one another, and so constitute what is termed a pollinium. The two contiguous pol- linia of adjacent anthers are united by horny rods (x) which converge upward and join with a horny dark body (j/) known as the corpusculum, which is hollow and has a slit along its outer face. This slit is relatively broad at the bottom, and tapers toward the top, thus forming a clip in which the feet of the insects get caught. Between each pair of anthers there is a deep recess closed by two vertical lips which stand wider open at the bottom than at the top, and the recess also narrows at the top. The opening between the lips at FIG. 107. AscZepias cornuti. Flowers. corpus- the top stands exactly beneath the slit in culum. The surface of the flower is slippery, so that when a bee, for instance, visits it, a good foothold is not ob- tained until the bee slips Its foot into the recess be- tween the anthers, termed the stigmatic chamber (m). Having obtained a foot- hold, the bee thrusts its sucking apparatus into the hollow nectar receptacle and obtains the nectar which has invited it to the flower. When the bee, however, seeks to go to another flower, its foot slips upward and becomes caught in the slit in the corpusculum. A struggle now ensues which usually FIG. 108. Diagram of a flower of Asclepias cornuti. , surface view of a flower, showing the opening into the stigmatic chamber at m, the upward-pointing nectar recep- tacles, and the reflexed petals. F, longitudinal diagram of a flower ; s, sepal ; p, petal ; n, one of the pistils ; r, stamen and nectar receptacle growing from it ; o, pollen sac ; v, nectar receptacle, with stigmatic chamber between it and the cavity containing the pistils. G, cross diagram of a part of a flower ; m, stig- matic chamber; o, pollen sac; n, apices of the pistils. H, diagram showing the relation of the pollinia to the stigmatic chamber; w, pollinium ; x, connect- ing rod or retinaculum. y, corpusculum or clip. The pollinia are in the pollen sacs and the clip stands over the stigmatic chamber. /, semi-diagram- matic view of a flower, showing the pollinia in position (as if the pollen sacs were transparent) ; outline of pollen sacs shown with dotted lines ; at the top of the pollen sacs are slits through which the pollinia are to be pulled out. J, showing the pollinia partly removed from the pollen sacs. WISE. 194 Introduction to Botany. results in the bee pulling the two pollen masses, united to the corpusculum, through the narrow slits (as in / and J) at the tops of the pollen sacs ; and thus laden, it seeks another flower, and there slips its foot, together with the pollen masses, into the stigmatic chamber. Now when the bee attempts to leave the flower, the pollen masses become tightly wedged at the narrow apex of the cham- ber, and a hard pull is required to break them loose from the foot. Finally, as the foot is being drawn from the stigmatic chamber it catches into the cor- pusculum directly above and pulls out a second pair of pollen masses. Thus the bee goes from flower to flower and from plant to plant, repeatedly pulling pol- Photograph of a honey bee gathering . nectar from an Asdepias flower, len masses from their sacs and One leg is still fast in a stigmatic depositing them in the stigmatic chamber of the flower last visited. chambers. Figure 109 is a pho- tograph of a honey bee gathering nectar from Asdepias flowers. One of the hind legs is still held in the stigmatic chamber of the flower which the bee has just deserted. Referring to Diagram G, note that the pollinia are re- moved by the bee from the pollen sacs o, o, and de- posited in another flower in the stigmatic chamber m. The bee always inserts its foot in m both in removing the pollinia and in depositing them. While the honey bee is the most important cross pollina- tor of this plant, butterflies and wasps are also of service. After the pollinia have been deposited in the stigmatic FIG. 109. Flowers. '95 FIG. no. Photograph of a Cabbage Butterfly caught by its legs in the corpuscula of two Asclepias flowers and unable to escape. chamber, they put forth pollen tubes which penetrate to the tips of the styles, and then turn down- ward and find their way to the ovules. A useful insect is rarely held in captivity by the flower, while weak insects, or their legs which have been pulled off in their strug- gle to free themselves, are often found hanging to corpuscula that have not been removed from their original places. Figures no and in illustrate instances of this kind. Rarely, indeed, a honey bee, too eager in its search for nectar, becomes caught in many flowers at once, and is unable to extricate itself (Fig. 112). Figure 113 is a photo- micrograph of a pair of pollinia attached to their common corpusculum, and Figure 114 is a photograph of a bee's leg with four corpuscula and two pollinia attached. There the second corpusculum has caught on one arm from the first, and so on. \ \ FIG. in. Photograph of a Moth with its legs caught in the corpuscula of three Asclepias flowers, one leg having been pulled off in its vain efforts to extract the pollinia and escape. 196 Introduction to Botany. 141. Cross Pollination of Yucca. Thus far we have taken for our illustrations flowers which are more or less profoundly modi- fied to secure cross pollination as a necessary incident attending the visits of insects. We shall now examine an instance of quite another character, and in some respects even more wonderful ^^^_ than those which have been FIG. 112. described. The flowers of the Photograph of a honey bee that has genus Yucca, representatives of died from exhaustion in its efforts . to free itself after its legs had been which are commonly found in gardens, depend almost entirely upon the Pronuba moth for their pollination. The structure of the flower is very simple and readily understood. The perianth is of the lilia- ceous type, there being three sepals and three pet- als, all of a creamy white color. In some of the Yuccas these droop for- ward and form bell-shaped flowers, while in others they are more widely Spreading. The Six Sta- Photomicrograph of a pair of pollinia of As- mens Consist Of fleshy, cle P ias cornuti attached to their corpuscu- . lum, as they appear when withdrawn from OUtward-CUrving filaments their pollen sacs. Photographed by trans- mitted light, and on account of the opacity of the corpusculum the slit in it is not shown, but a portion of a leg of a small insect is pendent from the slit. The pollen grains of which the pollinia are composed can be made out. X 15. surmounted by small an- thers. The pistil extends beyond the stamens, and the three carpels are im- Flowers. 197 perfectly united at the top, leaving a tube entirely open at the apex. The inner surface of this tube is stigmatic. The stigmatic tube does not open directly into the cavities of the ovary, but sends off three very narrow branches, each of which communicates with the cavity of a carpel. Accordingly, when pollen is once deposited on the inner surface of the main stigmatic tube, the pollen tubes find easy access to the ovules in each of the three carpels. The pollen is sticky and hangs together in masses, so that it is not adapted to being carried by the wind, and it is apparently impossible for it to get to the stigmatic tube without some outside agent. A small amount of nectar is secreted, but it is excreted at the very base of the pistil, so that insects seeking it would be far removed from the stigmas. Indeed, the low position of the nectar would seem rather to lead insects away from the stigmas. The flowers are borne in compound racemes high aloft on a strong woody shaft, and, because of their rather strong odor when new buds are opening in the evening and their white color, they are quite certain to make their presence known to insects flying in the twilight (see Fig. 115). If we take these facts as our clew and attentively watch these flowers about eight o'clock in the evening, the method of cross pollination will be made clear. A white moth, FIG. 114. Photomicrograph of the leg of a honey bee with a chain of four corpuscula clinging to it. The last two corpuscula are still bear- ing one pollinium each; the re- maining six pollinia have doubt- less been deposited by the bee in stigmatic chambers. X 5. 198 Introduction to Botany. known as the Pronuba moth, is seen to mount a stamen, scrape together the sticky pollen, and pack it against the under side of its head by means of a spinous structure known as the maxillary tentacle, which seems to have been specially developed for this purpose, for in other moths it FIG. 115. Yuccas in the twilight. Drawn from a photograph. is a mere vestige. In gathering the pollen it hooks its tongue over the end of the stamen, evidently to secure a better hold (see Fig. 116). Having become well loaded with pollen, as shown in the photomicrograph of the moth's head (Fig. 117), it descends the stamen and flies to another flower. There it places itself on the pistil between two of Flowers. 199 the stamens (see Fig. 118) and thrusts a slender ovipositor through the wall of the ovary and into the cavity occupied by the ovules. Having deposited an egg, it ascends the pistil, and by means of the maxillary ten- tacles and tongue, which at other times are coiled around the load of pollen, as seen in Fig. 117, it rubs ^ FlG Ii? pollen down the inner jPktf Photomicrograph of the head surface of the stip-- * and fore part of the body of g FIG 116 a Pronuba moth, showing the matic tube. Figure p ronu bamoth g ath- tongue and maxillary tentacles 119 is a flashlight ering pollen. | k e U netth thT?id f P x6 n photograph of a moth performing this act. The moth then descends the pistil, and standing between another pair of stamens it deposits another egg within the ovary ; then it ascends the pistil and rubs pollen on the stigmatic surface as be- fore. This process is re- peated until it may be that each of the six lines of ovules is provided with an egg, and the process of pol- lination has been as many FlG - II8 - times accomplished. Pronuba moth depositing its eggs in the The f u \\ meaning of this ovary of a yucca flower. Flashlight photograph taken about 8.30 P.M. WOndertul SCriCS OI Opera- 2OO Introduction to Botany. tions will not be understood until subsequent developments have been followed. Since the process of pollination has been so thoroughly done, most of the numerous ovules become fertilized and the seeds begin their development. In the meantime the moth eggs hatch into larvae, which find their food in the developing seeds. But the seeds are so numerous that the larvae reach their growth, gnaw a hole in the seed-pod and escape, while many uninjured seeds still remain in the pod. The larva spins a thread by which it de- scends to the ground, and, burro wing beneath the sur- face, it passes the winter in its pupal state, emerging as a fully developed moth at the time of the flowering of the Yucca the following summer. It appears that the mature moth takes no food, unless it secures some of the nectar of the Yucca blossoms in which it is wont to pass the day, with its head close to the bottom of the flower where the nectar is excreted. It does not eat the pollen which it gathers, and it seems cer- tain that it is prompted to place the pollen in the stigmatic tube after each act of oviposition solely by the instinct to provide for its young ; for it is readily understood that if the ovules are not fertilized the seeds would not develop and the larvae would be without food. The Yucca flower, instead of having elaborate devices FIG. 119. Pronuba moth rubbing pollen down the stigmatic tube of a yucca flower. Flash- light photograph taken about 8.30 P.M. Flowers. 201 to secure cross pollination, simply prohibits self pollina- tion by its tubular stigmas and its relatively short and reflexed stamens; and then, the sticky pollen and an abundance of ovules being provided, the performance of pollination is intrusted to the wise instinct of the Pronuba moth ; and not pollination simply, but cross pollination, for it has been noticed that it is the habit of the moth after securing the pollen to fly to another flower before it begins to lay its eggs. We wonder how such an instinct could have been evolved, and how the moth and the plant came to be so intimately associated and so absohitely necessary to each other's existence. It seems certain that they have come through the long years of their race history together, and that each has been affected by the modifications of the other. Sufficient illustrations have now been given to show the student that there is a wide and attractive field for study in the structure and behavior of flowers ; for they afford us not only the best evidence of the relationships of plants (see Chapter XVII), but they also reveal to us a mutually beneficent association of plants and animals, and the mar- velous plasticity of plants in molding the forms of their parts and responding to external forces and internal condi- tions in such a way as to meet any required end. 142. The Morphology of a Flower. In doing the work in the chapter on Modified Parts, the student has become familiar with the methods of seeking out morphological evidence, and he should now test, with all the evidence obtainable by him, the following statement of the morphol- ogy of a flower: A flower is a branch with much shortened internodes (termed the receptacle) whose growth in length is terminated by the production of spore-bearing leaves (stamens and carpels); the most complete flowers also having modified leaves in the form of sepals and petals. 102 Introduction to Botany. In order to understand the morphology of the parts of a flower we must refer back to simpler and older types of vegetation. The Lycopodiums or club mosses are repre- sentatives of an ancient group of plants which reached its maximum development in the Carboniferous period. There are good reasons for the belief that the Lycopodiums and the flowering plants are offshoots from a common ancestral stock, the Lycopodiums be- ing, of the two, much less modified and more primitive in character. We find in them that the stem is thickly beset with small, awl-shaped leaves (Fig. 120). Near the apex of the stem some of the leaves bear spore cases or sporangia In FIG. 120. gregated into cones at the apices of species the Spore-bearing the branches; 2, a leaf from the cone, , 1 7 ,, with a sporangium in its axil ; 3 and leaves Or Sporophylls are 4, spores from the sporangium. After broader and longer-pointed WOSSIDLO. if - f .. , than the foliage leaves, but there may be all degrees of gradation between the two forms. In other species there may be no difference in appearance between the foliage leaves and sporophylls. In some species the sporophylls are aggregated into a cone, in others not. In the Lycopodiums the sporangia and spores are of one kind only; but in the somewhat nearly related genus Selaginella, there are two sorts of sporangia, borne each on the stem in the axil of the sporophyll, which in general Flowers. 203 m does not differ from a foliage leaf in appearance. One kind of sporangium contains relatively small spores termed microspores (Fig. 121) which on germination give rise to a rudimentary plant body called prothallium, bearing sperm cells ; and the other sort of sporangium contains relatively large spores, the macro- spores (Fig. 12 1), which on germination produce a prothallium bearing egg cells. The sporangium containing macrospores is termed macrosporan- gium, and the sporophyll subtending it macrosporo- phyll, while the corre- sponding parts relating to the microspores are called micro sporangium and mi- crosporophyll. Now, in a flower, since the pollen grain produces the sperm, it must be a microspore, the anther a microspo- rangium, and the entire stamen a modified microsporophyll. The large cell in the ovule (termed embryo sac} which pro- duces the egg must be the macrospore, and the ovule the macrosporangium, while the pistil evidently corresponds to a macrosporophyll with the edges infolded and grown together forming an inclosed chamber. Each sporophyll taking part in the formation of a pistil is called a carpel. Or the pistil may be composed of more than one sporophyll united, as indicated by the number of styles, stigmas, or groups or rows of ovules. When composed of a single sporophyll or carpel the pistil is said to be simple, when of FIG. 121. i, Selaginella. Toward the summit of the plant the leaves are more pointed, and they become aggregated into a cone-like group at the apex. 2, Microsporangium, m, discharging microspores ; n, macrosporan- gium containing macrospores. After STRASBURGER. 204 Introduction to Botany. FIG. 122. Transition between stamens and petals in Nymphcea odorata. After GRAY. more than one, compound. The sepals and petals may be either modified foliage leaves or barren sporophylls. Evi- dence that they may be the latter is found in the fact that all gradations of transition between sta- mens and petals occur in the sweet-scented pond lily, Nymph&a odorata (Fig. 122), and in various double flowers. But on the other hand all de- grees of gradation may be found from foliage leaves, through sepals and petals to stamens, so that along this line of evidence we cannot come to a positive conclusion. Since in the relatively ancient - Lycopodiums and Selaginellas there may be no difference in appearance between the foliage leaves and sporophylls, and in others there may be all degrees of gradation between them, it would seem that foliage leaves and sporophylls have had a common origin. The relative positions of the different parts of flowers may show considerable variation, as seen in diagrams of row * V V c FIG. 133. d a, yeast plants, some of them budding; b, micrococci (singular, micrococcus) from the air; c, Bacillus subtilis, showing internal spore-formation; d, bacilli (singu- lar, bacillus) of Asiatic cholera, with motile flagella. Photomicrographs X 740. After GUNTHER. doubt. It is thought by some that the bulk of their bodies is made up of nuclear material. 153. Methods of Reproduction. Bacteria reproduce by division, one becoming two, two four, and so on. Asexual spores are also formed, either by the ordinary cells pro- 258 Introduction to Botany. duced by division assuming a spore character, or by the cell contents rounding off, expelling water, and entering into a condition in which great extremes of heat, cold, and desiccation can be withstood (see Fig. 133, c). While in the vegetative state, most bacteria are killed at a tempera- ture of 65 C, their spores can stand 100, or in some cases 130 C., of dry heat; but no spores can withstand an air-free steam heat of 120 C. for half an hour. This high temperature is achieved by generating the steam under ij atmospheres' pressure in an apparatus known as an autoclave. The spores are very resistant to cold ; freezing does not affect them, and they have been known to survive even after exposure for a short time to the temperature of freezing oxygen, namely, 213 C. below zero. By a process known as discontinuous heating they may be killed at 100 C. By this method the heating is carried on for half an hour on each of three consecutive days. The explanation of the success of this process is that most of the spores which resist the first heating will probably have germinated, and so have passed into a less resistant state, by the time of the second heating. The third heat- ing is certain to destroy the remaining bacteria, since all of the spores will have germinated by that time. 154. Forms of Bacteria. In form, bacteria are round, oblong, rod-shaped, or spiral (Figs. 133-134). But while exceedingly simple in the construction and contour of their bodies, the results of their activities are quite diverse, and of vast importance to other plants and animals. 155. Nutrition of Bacteria. Although bacteria may pro- duce pigments of various colors, they do not form chloro- phyll and cannot obtain their living by employing the energy of 'the sunlight to build their food ; they must, Slime Moulds, Bacteria, and Yeasts. 259 therefore, live upon materials already organized, or they must utilize some source of energy other than the sunlight for the construction of their food. Most bacteria have adopted the former course, and obtain their sustenance from FIG. 134. e, bacilli of typhoid fever ; f, bacilli of chicken cholera ; g, bacilli of splenic fever ; h, spirillum of recurrent fever, and red blood corpuscles. Photomicrographs X 740. After GUNTHER. the bodies or products of plants and animals. Others, however, are able to induce the oxidation of compounds of nitrogen, sulphur, iron, etc., and appropriate the heat thus produced for the fixation of carbon from carbon dioxide, much as green plants do by means of the sunlight. To 160 Introduction to Botany. show the importance of bacteria in the economy of nature, a brief statement will be made of some of the things which are known to be accomplished by them. 156. Bacteria of Economic Importance. There are forms existing in the soil, known as nitrifying bacteria, which bring about the oxidation of certain nitrogen compounds brought down by rains or resulting from the decay of plant and animal bodies, nitric acid being produced, a sub- stance absolutely necessary to the nutrition of plants. Its production by the bacteria is of great importance, since it exists in the soil in relatively minute quantities and is easily carried away by percolating water. Bacteria of another kind inhabit the root tubercles of leguminous plants, and, taking the free nitrogen of the air, build it into the constitution of their own bodies. Finally the bacteria appear to be digested and appropriated as food by the leguminous plants (Fig. 13). In this way the green plant is able to obtain indirectly the free nitrogen of the atmosphere, which otherwise would be inaccessible to it. A knowledge of these facts is of utility to agriculture, for land naturally poor in nitrogen can be sown to alfalfa or plants of similar character, which, when plowed under, leave the land much richer in nitrogen than it was before. It has been found practicable to inoculate with liquid cultures of the bacteria soils which do not naturally contain them. The importance of these bacteria to leguminous plants grow- ing in soils poor in compounds of nitrogen is shown by the experiment illustrated in Fig. 135. Other forms are instrumental in the production of vinegar from alcohol, in the proper ripening of cheese, and others add to the agreeable flavor of butter, as has been efficiently demonstrated in the dairies of Finland and Denmark. 157. Disease-producing Bacteria. There are other forms Slime Moulds, Bacteria, and Yeasts. 261 which are injurious instead of beneficial, such as those pro- ducing consumption, diphtheria, typhoid fever, lockjaw, blood poisoning, bubonic plague, etc. (Figs. 133-134). These diseases are brought about by poisons produced by the bac- teria within the body. Great advances in surgery and in the treatment and prevention of dis- eases have been made by an un- derstanding of the life history and habits of these microscopic forms of life. It is now known, for instance, that gangrene and blood poisoning, which formerly often followed in the wake of surgical operations, were brought about by bacteria clinging to the surgeon's knife, or which were in the water, bandages, etc., used in dressing the wound. Now every instrument or object em- ployed in such operations is thor- oughly sterilized, and the healing of the wound goes forward with- out complications. So, too, it is now known that the expectorations of consumptives and the dejecta of typhoid patients are teeming with the bac- teria causing these diseases, and that unless the bacteria are destroyed by suitable poisons or heat they may spread disease. 158. The Nature of Yeasts. Yeasts are low forms of plants which, like bacteria, are destitute of chlorophyll, and are dependent for their food upon materials built up FIG. 135. Experiment showing the impor- tance of nitrogen-fixing bacteria to leguminous plants, t, peas grown in a nitrogen-free soil with bacteria; u, the same in all re- spects, but without bacteria. Af- ter FRANK. 262 Introduction to Botany. by green plants. They are rounded or ellipsoidal (Fig. 1 33> a \ an d are about .0015 to .015 millimeter in diameter. Each individual consists of a single protoplast, surrounded by a delicate wall. Investigation into the life history of yeasts seems to have shown that they are really spore-like forms which have been produced by certain species of filamentous Fungi, but however this may be, the yeasts are capable of sustaining an independent existence, and of multiplying both by budding and by internal spores. 159. Reproduction of Yeasts. In budding, a knob-like outgrowth is produced which finally becomes separated and grows to the size of the individual from which it sprang. In internal spore-formation, the cell protoplasm breaks up into several rounded bodies that escape and finally germi- nate, producing forms like the one from which they sprang. The internal spores are apt to be formed when the food is running short ; and they are evidently useful in tiding over unfavorable conditions. 160. Yeasts in Bread-making. Yeasts obtain part of their food from weak solutions of sugar, and in so doing convert the sugar into alcohol and carbonic acid ; their usefulness in the raising of bread is due to this action. When the sponge is made, the ferment known as diastase, which was produced in the grain of wheat for the purpose of digesting the starch when the seed germinates, carries on the process of starch digestion in the sponge, changing a part of the starch into grape sugar. Then the yeast plants begin their action on the sugar, and the carbon di- oxide produced along with the alcohol becomes entangled in the sticky mass and causes it to puff up. If, now, while the gas is still forming, the flour is worked in with the sponge, the gas is produced at all points throughout the mass of dough and raises it. The alcohol which is produced Slime Moulds, Bacteria, and Yeasts. 263 at the same time is driven off in the process of baking. If the bread is allowed to stand too long before baking, the alcohol is attacked by bacteria which change it into acids, and the dough is soured. 161. Yeasts in Alcoholic Fermentation. There are vari- ous sorts of yeasts which produce alcohol, and some other little-known substances that give flavor, bouquet, etc., in the manufacture of beer, wine, and other fermented liquors. In recent years these various kinds of yeasts have been grown separately, and are used in the production of distinct kinds of beer and wine. Some yeasts seem also to be the cause of disease in man and the lower animals. CHAPTER XII. ALGJE, FUNGI, AND LICHENS. PROVIDING MATERIALS. Algae and Fungi should be gathered in both vegetative and fruiting conditions and preserved in formalin. Many of , the fresh- water Algas do well in glass jars of water kept in a well-lighted place in the labora- tory. Spirogyra and Oedogonium are very amenable to this sort of treatment. Reproductive stages will be found in abundance in early spring and summer. Vaucheria can usually be obtained in greenhouses, growing on flower pots, etc., at any season of the year. Out of doors it should be sought on moist and shady banks near the water's edge ; and when found in good condition to show the method of sexual repro- duction it should be preserved in formalin. One may secure Pleurococcus at any time of the year on the shady side of trees, etc., bread mould and Fungi, of a similar character as directed under Observation 160, and rusts, smuts, and mildews in great abundance at almost any time during the growing season. The last may be preserved either dry, in forma- lin, or in 70% alcohol. Toadstools and their kind can be collected in pastures and open woods at any time during the growing season when the weather is not too dry. Lichens are to be found on trees, old fences, and on rocks at any time. OBSERVATIONS. ALG.E. 151. Cut, from the north side of a tree, bark which is covered with a green mealy growth ; moisten with water, and place on wet filter paper under a bell jar for several hours. Observe the character of the growth, first with the naked eye and then with a simple lens. Scrape up 264 Algae, Fungi, and Lichens. 265 some of it with the point of a knife, and notice whether it readily breaks up into small particles. Observe the tree on which it was growing. Is the growth always on the north side ? How far up the trunk does it extend ? 152. Scrape up a small portion of the growth with the point of a knife, taking care not to remove the bark, and mount under a coverglass in a drop of water. Place a clean cloth over the forefinger and move" the coverglass about gently, in order to spread out the preparation in a thin film. If the pressure of the finger is too great, the little plants will be broken. Examine with a high power, and pick out what appears to be a single individual. How do you account for the clusters of individuals which are found ? Does the green color occur in definite chloro- plasts ? Treat the preparation with chloral hydrate-iodine. Does starch appear ? Is there any difference in this respect between material which has been kept in the dark and that which has been exposed to the bright light of the northern sky, but not to the direct rays of the sun ? Can you tell why some trees seem to possess this growth more than others ? 153. Examine some of the green filamentous plants which occur in ponds, lakes, or small running streams. Do they float freely in the water or are they fastened down in any way ? How do you account for the bubbles of gas which collect about these plants in the sunlight? Is there any difference in this respect between plants which are freely exposed to the sun and those which are deeply shaded ? If so, what is the significance of the difference ? 154. Pick up some of the material and spread it out in the hand. Can you distinguish the individuals of which it is composed ? Can you distinguish the parts of which the 266 Introduction to Botany. individuals are composed ? Leave some of the plants out of the water for a time, and note what occurs to them. 155. Spread out a few of the individuals in a drop of water under a coverglass and examine with a medium power of the microscope. Do the parts of which the individuals are composed differ from each other in any essential way ? Note the character of the walls and of the contents. Is a nucleus to be seen ? What is the form of the chloroplasts ? . Treat a preparation with chloral hydrate-iodine, and note whether starch is demonstrated. Does the nucleus become more prominent for a time while the protoplasm is dissolving ? 156. Examine some of the green, filamentous, felty growth which abounds on moist shady banks. Is it ever found in sunny situations ? Examine some of the fila- ments, and try to determine how they are held together to form the felty mass. Are they anchored to the earth, or do they simply grow over its surface ? 157. Mount some of the filaments in a drop of water under a coverglass. Are they composed of cells, or does each filament appear to be one large cell? Locate the chloroplasts. Can more than one nucleus be found ? 158. If living near the seacoast, observe the bladder- wrack. How is it fastened to its substratum ? Is there any special device to' keep the free parts buoyed up in the water? Examine the enlarged ends and press them be- tween thumb and finger while observing them with a lens. Make thin sections through the swollen pitted ends, mount in a drop of water under a coverglass, and examine with a medium power. Small cavities, or conceptacles, should be seen opening exteriorly. In our common bladder-wrack, Fucus vesictilosus, these cavities will be found to contain either the eggs or the sperms, this species being dioecious. Algae, Fungi, and Lichens. 267 159. Make sections through the enlarged bladder-like portions of the plant. Do they contain air or water ? What is their evident purpose? Make sections through the other portions of the plant, and examine under the microscope. Although the plant has a brown color, it really contains chlorophyll, whose character is masked by the brown coloring matter associated with it in the chloro- plasts. By what means is this plant held in proper condi- tion to catch the sunlight ? FUNGI. 1 60. Moisten stale bread in water and place it under a bell jar in a warm place. To be more certain of obtaining what is wanted, place under the bell jar some lemon pulp and rind from which the juice has been squeezed, of pieces of partly decayed sweet potato or banana. Various sorts of growths will appear, but the filamentous growths which in a few days bear minute spore cases on thread-like stems, are the forms desired for this study. 161. Determine whether the filaments making up the body of the growth penetrate the substratum or simply lie on its surface. Examine with a lens the spore cases, or sporangia, of different ages. With a pair of forceps, care- fully pull off sporangia of different stages of development, and mount under a coverglass in a drop of 70^ alcohol. (Alcohol is used instead of water because air bubbles adhere to the material when water is used, but after mount- ing in alcohol a drop of water may be placed on the slide in contact with the coverglass, and as the alcohol evapo- rates the water will take its place.) Note the appearance of the spores in the sporangia of different ages. Why do the old sporangia appear black ? 162. Soak a cubical block of stale bread in water, sow 268 Introduction to Botany. spores from the old sporangia over all sides of it, and keep it in a moist atmosphere under a bell jar. When the sporangia appear, note whether they all stand upright, or whether the direction taken by them bears a definite relation to the surface of the bread. Expose them to the light so that they will be illuminated on one side more than on another, and note whether the direction taken by the stems which bear the sporangia is affected in any way. 163. Examine the surface of a rusted leaf of wheat, oats, or any of the wild grasses. Does the rust appear on the veins or between them ? Examine with a lens and note whether the epidermis of the leaf has been broken by the rust. Can any growths not belonging to the leaf be seen ? 164. Make thin sections of the leaf across the rusted spots, and mount under a coverglass in a drop of water. If the leaf is dry, soak it for a few hours in water before sectioning. The section of the leaf should be so thin that the spores of the rust and the cells of the leaf immediately beneath may readily be seen. The parts may be rendered more transparent by mounting the section in a saturated solution of chloral hydrate. Notice the course of the thread-like part of the rust which penetrates the interior of the leaf. 165. Does the rust appear to produce any serious mechanical injury to the tissues of the leaf ? In what ways is the injury to the plant probably produced? Does the rust appear to have any means of manufacturing its own food independently of the plant on which it is growing ? What have you observed in regard to the ravages of rust in wheat fields, etc. ? 1 66. Examine a toadstool growing in the woods or pasture. Dig away the soil carefully at its base to see Algae, Fungi, and Lichens. 269 what sort of connection it has with the substratum. Can smaller toadstools be found just above or beneath the soil ? 167. Break off the cap of the toadstool and lay it on a piece of blue paper where it will not be disturbed, and after a day or so remove the cap and note what has happened. 1 68. Make thin sections across the gills, and mount in a drop of 70^) alcohol, and with a high power look for the spores growing from the gills. Examine with the same power some of the deposit found on the paper of Observa- tion 167, and compare with the spores found growing to the gills. 169. Examine the bark of old trees in a wood for the discolored spots and scale-like growths known as Lichens. Is the body of the Lichen all alike, or does some part appear to be spore-bearing ? Cut off the Lichen from the bark and soak for a day in water, then make thin sections through the spore-bearing part and mount in a drop of water. Of what is the body of the Lichen found to consist ? Are there any parts containing chlorophyll ? Observe the slender sacs in which the spores are borne. How do Lichens probably obtain the water necessary to their growth ? Do they make a slow or a rapid growth ? DISCUSSION. ALG^; 162. Nature of Algae. The Algae, of which we have seen examples in the green growth on trees, in the filamen- tous green growths in water and on shady banks, and in the bladder-wrack of the ocean, are low forms of plants of very simple construction, except in the case of the larger seaweeds. They consist for the most part of single cells, or of rows of similar cells joined end to end to form fila- ments. They contain chlorophyll, and so are able to make 2JO Introduction to Botany. use of the carbon dioxide of the air, or of the water in which they reside, in the same manner as do the more complex green plants. Having need of the sunlight, they usually float near the surface if their habitat is water ; but if they live on the land, they are adapted only to moist and shady situations. They have no waterproof protective covering such as is furnished by the cuticle of the higher land plants, and accordingly quickly dry up if exposed to a dry at- mosphere. 163. Pleurococcus Viridis. Pleurococcus viridis, which we found as a mealy green growth on the north side of trees, is one of the simplest of the Algae. As has been seen, an individual con- sists of a single globular cell, having an outer transparent wall of cellulose, a nucleus which is difficult to see, and a few, rela- tively large chloroplasts occupying the bulk of the cell (Fig. 136). This single, minute individual is equipped to sustain an independent existence, being able to perform within its small compass the necessary nutritive and reproductive functions. But since it consists of a single cell, it is unable to construct special systems for the separate func- tions ; and it is therefore restricted to habitats which by their nature protect it against too great transpiration, the beating of storms, and other sources of mechanical in- juries. The thin and delicate wall necessary to allow the ingress of its raw food materials will not permit it to exist in places which are dry or fully exposed to the sun. We may FIG. 136. Pleurococcus viridis. a, a single individual ; b, c, and d, various stages in cell division. The chloroplasts are so crowded that no attempt has been made to distinguish them in the figure. Algae, Fungi, and Lichens. 271 look upon it as one of the simplest forms which have essayed to appropriate the energy of the sunlight for the manufacture of their food; and it, or some form not dis- tantly related to it, probably represents the very primitive organism from which the higher plants have been evolved. Pleurococcus multiplies by cell division, one becoming two, two four, etc., as in the case of the bacteria. When examined under the microscope, the individuals are usually found adhering in groups in a manner which suggests that they are on the border land of unicellular and multicellular forms. 164. Spirogyra. Among the forms of filamentous Algae taken from fresh water, Spirogyra and Oedogonium are quite likely to occur. The method of reproduction of Oedogonium has already been described on page 163, and Spirogyra (Fig. 137) will now be used as a type of fila- mentous Algae. Each individual consists of similar cells joined end to end. The cytoplasm lines the cell wall, leav- ing a large vacuole filled with cell sap. Embedded in the cytoplasm are one or more elongated and spirally coiled chloroplasts. A rather large nucleus is suspended at the center of the cell by arms of cytoplasm which extend to certain bodies, known as pyrenoids, embedded in the chloroplasts. When a filament is mounted in a drop of chloral hydrate-iodine, starch is found to be clustered about the pyrenoids, and at no other places in the chloroplasts. We may conclude from this that while the chloroplast is undoubtedly manufacturing food throughout its whole body, the pyrenoids are the centers of accumulation of reserve materials in the form of starch (Fig. 137). When actively growing filaments are kept in the dark for a few days, the starch disappears. The chloroplasts utilize the sunlight in the same manner as do the chloroplasts in the 272 Introduction to Botany. leaves of higher plants. The student may be able to per- ceive some advantage in the spiral course of the elongated chloroplasts with reference to the absorption of light. All cells of the filamentous individual perform the same nutritive functions ; any one of them may take part in the formation of spores ; and all bear prac- tically the same relation to the outer world. The exterior wall of the filament, and the partition walls between the cells, are of cellulose, and permit liquids and gases to pass readily through them. Since they possess no waterproof cover- ing, the filaments quickly dry up when taken out of the _v water. Being buoyed up by the water and freely floating in it, very little stress is ever exerted on the filaments, and special strength- ening devices are unnecessary. 165. Repro- duction of Spi- FiG. 137. v, a single cell of Spirogyra, showing the spiral chloro- plasts containing numerous rounded pyrenoids. The nucleus is suspended at the center of the cell, w and x, two conjugating filaments ; at i, an early stage in the formation of a connecting tube between the two cells; at 2, the tube has formed and the protoplast from a cell of filament w is passing into the corresponding cell of filament x and is fusing with its protoplast ; at 3, a later stage ; at 4, a spore has formed from the fused proto- plasts. After SACHS. rogyra. Spirogyra shows a degree of sexuality in the method of its reproduction. Two filaments which happen to be lying in close proximity put forth outgrowths from one or more of their cells which finally meet, and the walls separating them become absorbed. The entire protoplast Algae, Fungi, and Lichens. 273 in the conjugating cell of one filament passes through the tubular connection and fuses with the protoplast in the conjugating cell of the other filament, all of the conjugat- ing cells of one filament being receptive, and of the other contributive. The two fused protoplasts organize a wall about themselves, and become a resting spore which is able to endure desiccation and other adverse conditions. After a period of rest the spore germinates and produces a filamentous individual similar to those from which it sprang (Fig. 137). The filament which bears the spores may be considered the female and the other the male, but there is no structural differentiation into egg and sperm. 166. Vaucheria. Vaucheria is a filamentous Alga of another character. It grows either in water or on moist and shady banks. Each individual is a tubular branched filament which in its vegetative state is not divided by cell walls. One end of the filament is modified in such a way as to serve as an anchor to the substratum (Fig. 138). The protoplast which lines the tubular filament contains many nuclei and probably consists of many fused protoplasts. Small rounded chloroplasts are found in great numbers in the filaments. The wall is of cellulose without much waterproofing, and the plant cannot flourish away from water or moist places. The branched filaments have the habit of interweaving, and so furnish each other mutual support. 167. Reproduction of Vaucheria. Vaucheria reproduces by both the sexual and asexual methods. In the latter process the protoplasm accumulates in a swollen end of the filament, which becomes demarked from the rest of the filament by means of a transverse wall. The swollen end breaks open and the mass of protoplasm passes out and swims about for a time by means of numerous cilia that 274 Introduction to Botany. grow out over its surface. Soon it comes to rest and organizes a wall over its surface, and after a brief period it germinates, producing a new branched filament, with an expansion at one end for anchorage to the substratum. In the sexual method of reproduction, two forms of out- growths are produced on the same filament ; a rounded FIG. 138. Vaucheria sessilis. i, a filament-bearing oogonia (c) and an Antheridium (d). The rounded portion to the left represents the spore from which the filament has sprung. The clear branched portion is a clinging organ by which anchor- age is made with the substratum. 2, a germinating spore. 3, a later stage. 4, an asexual spore escaping from its parent cell. 5, the same after it has come to rest and surrounded itself with a cell wall. 6, the spore, (5) in the first stage of germination ; 2 and 3 are later stages. After SACHS. one (the oogonium), which is separated from the parent filament by a wall, and contains the egg, and . a slender outgrowth (the antheridium\ containing the sperms at its apical portion (see Fig. 138). The cells containing the egg and those containing the sperms break open at their apices, and the sperms swim out by means of two cilia Algae, Fungi, and Lichens. 275 with which each is provided, and, seeking the egg, one of them fuses with it and accomplishes its fertilization. However, proterandry may occur, so that the egg is often not fertilized by sperms from the neighboring antheridium. The egg while still contained within its cell then produces a thick wall about itself, and passes through a resting period before germinating. Vaucheria is a step in advance of Spirogyra in the evolution of sexuality, for its repro- ductive elements are quite sharply differentiated into egg and sperm. 168. Fucus. The large brown marine Alga known as wrack-weed or bladder-wrack (Fucus vesiculosus) grows anchored to the rocks between high and low tide levels. Its branches are somewhat flattened, and possess air bladders which buoy it up in the water, and thus enable it to expose a broad surface to the light. It is multicellu- lar, and its tissues are somewhat differentiated, the central part consisting of slender cells with large spaces between them containing mucilage, and the outer tissues being made up of smaller rounded cells, the peripheral layer of which has the nature of an epidermis. Chloroplasts reside in the outer tissues, but their green color is modified by a brown coloring matter associated with the chlorophyll. Notwithstanding this, the chloroplasts of Fucus are active in photosynthesis and sustain the same relation to the sunlight in the manufacture of food materials as do the chloroplasts of green plants. 169. Reproduction of Fucus. Reproduction is effected sexually by the production of eggs and sperms, borne in minute cavities of the plant body, known as conceptacles (Fig. 139). In the species vesiculosus the sperms and eggs are borne in different plants, but in other species they both occur in the same conceptacle. The eggs, Introduction to Botany. eight in number, are borne in small sacs growing out from the walls of the conceptacle (see Fig. 139); and the sperms are formed in elongated cells produced on hair-like outgrowths. Both eggs and sperms become discharged FIG. 139. Fucus. A, portion of a frond ; B, section through a conceptacle ; C, oogonium with eggs ; D, antheridium with sperm cells ; E, an egg with sperm cells swim- ming about it. After THURET. from their conceptacles into the surrounding water, and the sperms seek the eggs, being able to swim about by means of two cilia. One of the sperms penetrates the egg and effects its fertilization. The egg then forms a wall about itself and is capable of immediate germination. Some of the marine Algae closely related to Fucus attain as much as a hundred feet in length, and produce lateral Algae, Fungi, and Lichens. 277 outgrowths resembling leaves and performing the functions of leaves ; so that both in the construction of the vegetative parts and in the method of reproduction we find in them close affinities to the higher plants. FUNGI. 170. Character of Fungi. Turning now to the fungi, we find plants which are characterized by their lack of chlorophyll, and a consequent inability to utilize the energy of the sunlight in the manufacture of their food. We find, therefore, that they are either parasitic or saprophytic, that is, they obtain their food from living or dead plants or animals. They are closely allied to the Algae in their structure and modes of reproduction, and may be their degenerate descendants. 171. Mucor, or Bread Mould. The common black bread moulds, Mucor mucedo and Mucor stolonifer, are good repre- sentatives of the saprophytic kinds of Fungi. The first- named Mucor is composed throughout its whole vegetative body of a much-branched unicellular filament which rami- fies partly through the substratum and partly over its surface, forming a somewhat felty coating. The wall of the filament is thin and permits the transfusion of liquids. The portion of the Fungus which is embedded in the sub- stratum excretes a ferment that renders organic substances soluble and adapted to absorption and assimilation. In this way the Fungus is able to devour the starchy and proteid substances of bread, vegetables, fruits, etc., and even the cellulose composing cell walls. Such ferments are extracted in large quantities from Fungi and sold on the market in the form of digestive extracts or tablets. 172. Reproduction of Mucor. Having accumulated a sufficient amount of food materials, it proceeds to form its Introduction to Botany. reproductive bodies. Portions of the branched filament become cut off by cell walls, and these demarked portions FIG. 140. Stages in the life history of Mucor mucedo. A, an entire plant bearing sporangia on upright stalks. B, i and 2, a sporangium before and after breaking open to discharge the ellipsoidal spores; 3, the upper part of the stalk after the sporan- gium has broken away ; 5, a germinating spore which is to produce a plant like A. C, i, two conjugating branches of the thread-like mycelium ; 2, a later stage, showing two end cells demarked by cell walls ; 3, a later stage where the wall separating the two end cells from each other has become dissolved, so that the contents of the two cells have fused to form a resting spore ; 4, the mature rest- ing spore ; 5, the germinating resting spore giving rise to a single sporangium bearing relatively few spores, as shown in B, 4. After BREFELD. send forth branches which grow outward from the sub- stratum, sometimes to a distance of several centimeters, Algae, Fungi, and Lichens. 279 and finally produce enlargements at their ends which become separated from the rest of the branch by a cell wall (Fig. 140). The protoplasm in these enlarged ends divides into many spores, which finally break out from the surrounding wall and become scattered, giving rise on their germination to new filamentous individuals. When the substratum supplies an abundance of food materials, resting spores may be produced sexually. In this process the ends of two branches meet, and a partition wall is formed in each, a short distance back from the ends. The end walls then become dissolved, and the con- tents of the short terminal cells fuse together, thus consti- tuting a single cell, which then enlarges considerably, produces a thick outer wall, and enters into a period of rest. When this sexually produced spore germinates, the thick outer wall becomes broken, and the inner wall and contents grow forth and produce a branched filament which sooner or later gives rise to asexual spores as above described (see Fig. 140). By the asexual spores, which are produced in almost countless numbers, the fungus be- comes broadly scattered, while the less number of sexual spores serves to carry the species through adverse condi- tions. 173. Rusts. The rusts on wheat and other grasses are interesting representatives of a large class of Fungi which obtain their living at the expense of other live plants. Observations 163 and 164 have shown us that the rusty streaks appearing on the leaves of wheat, for instance, are really masses of the oval spores of the fungus (Fig. 141, A) which break through the epidermis and become blown about by the wind. The spores are borne on the filamentous vegetative part of the Fungus (Fig. 141, B), which ramifies amongst the parenchyma cells of the leaf 280 Introduction to Botany. and appropriates the materials manufactured there. These spores, called summer spores, or uredospores, when brought A FIG. 141. A, clusters of uredospores of wheat rust breaking through the epidermis between the parallel veins of a leaf of wheat. B, a cross section through one of the spore clusters of A, showing the uredospores highly magnified. to other leaves by the wind, put forth slender sprouts which enter the leaf through the stomata, and thus within the leaf new rust plants are started, which in turn produce summer spores. Later in the season spores are formed which are two-celled, pear-shaped, and darker in color (Fig. 142) ; these, known as the winter spores, or teleutospores, survive parasitized by Puccinia. The mycelium of the fungus extends through the leaf and bears clus- the Winter, and the ters of teleutospores at the upper surface. following; Spring ger- minate and produce filaments, each bearing several small spores (Fig. 143) which may grow into the leaves of barberry FIG. 142. Photomicrograph of a cross section of a grass leaf Algae, Fungi, and Lichens. 281 bushes where these abound, producing chains of spores, termed aecidiospores, in cup-shaped cases (Fig. 144, B). These spores become discharged, and when blown to the surface of a leaf of wheat they grow into it, and finally summer spores appear at the surface of the leaf, as already described. It appears, then, that the rust of wheat produces three kinds of spores and requires two kinds of plants to run the full course of its existence. The winter spores, however, can establish themselves in the leaves of wheat without the intervention of the bar- berry, and the summer spores can also sur- vive the winter and reproduce the fungus on wheat the following spring. Other parasitic Fungi of common occur- rence which often do great damage to the plants of the field and garden are the srnuts and mildews. FIG. 143. Germinating te- leutospore of wheat rust. After TULASNE. FIG. 144. A, leaf of barberry bearing aecidiospores of wheat rust. B, cross section through the barberry leaf, showing groups of spores immersed in the tissue of the leaf. (B after DE BARY.) 174. Toad- stools. The toadstools are too commonly observed to re- quire descrip- tion here, and only a brief ac- count of their structure and ways of life will be necessary. The stem and 282 Introduction to Botany. cap are com- posed of multi- cellular fila- ments so closely woven and grown together as to form a false tissue (Fig. 145). On both surfaces of the gills minute spores are borne which become projected to the ground, as shown by Obser- vation 167. Or in some cases both cap and stem deliquesce, form- ing a fluid mass which engulfs the spores, and perhaps assists in their germination. When the substratum in which a toadstool is growing is carefully dug away, it is found that there are filamentous growths per- meating it from which the above- ground part of the Fungus has sprung. It is the underground FIG. 145. Agaricus campestris or mushroom. D, mature plant with stalk bearing an ex- panded cap, from which gills are pendent. G, a cross section of some of the gills, slightly magnified, and F, one of the gills in cross section more highly magnified, showing the gill to be fringed on both surfaces with stalks bearing spores. H, a more highly magnified detail of a portion of F, showing the rounded spores. E, young mushrooms, to become like D. After SACHS. Algae, Fungi, and Lichens. 283 FIG. 146. part that has accumulated the food necessary to main- tain the very rapid growth which toadstools are so well known to make. The student will notice by a careful examination of the sub- stratum that it is very rich in vegetable remains in the form of mouldering leaves, stems, roots, etc., whose substance the toad- stool is able to digest by means of ferments excreted from its un- derground filaments. But the toadstools and their allies do not always restrict themselves to this innocent mode of life, for it may happen that underground fila- ments, ramifying through the rich mould of a forest in quest of food, penetrate the roots of a tree, and Destruction by Fungi of a ceil . of pine wood. The branched entering the WOody tissues, digest filament is a part of the my- and appropriate them for food ceiium of the Fungus. The upper part of the wood cell (Fig. 146). So the Fungus advances deeper into the roots, and up into the stem, sapping their strength, until the tree may easily be broken off or upturned by the wind. These Fungi also gain access to the interior of the trees through wounds in the bark, or through the broken branches of the above- ground parts. (Figure 147 shows a portion of a trunk of a tree which has suffered from the ravages of Fungi.) In some localities forest trees suffer considerable dam- age from foes of this kind; and not only trees, but timbers also which have already been put to purposes .of construction. has not yet been disinte- grated by the Fungus, as has the lower dotted part. After R. HARTIG. 284 Introduction to Botany. Besides multiplying by spores, the toadstools may be disseminated by the separation of bits of the masses of filaments which occupy the sub- stratum ; in this way mushrooms are artifi- cially propagated. LICHENS. 175. Nature of Lichens. The Lichens afford a unique example of para- sitism by Fungi ; for a Lichen is not a distinct plant, but rather a com- munity of Fungus and Algae. The little Pleuro- coccus with which we are already acquainted is often associated with a Fungus in this way. The Fungus undoubtedly derives its food from materials man- ufactured by the Algae, but at the same time it does the Algae no bodily harm, except that which might result from the tax on their industry. It is thought by some that there is a fair exchange of benefits between the FIG. 147. Trunk of a tree in process of destruction by Fungi. Fungi belonging to the genus Poly- porus growing out from the trunk. Interior of the tree rotten and hollow and used as a nest by owls. FIG. 148. Different forms of Lichens. a, Parmelia colpodes ; b, Graphis scripta on bark of tree ; the elongated black spots are the Lichens ; c, Cladonia furcata. Algae, Fungi, and Lichens. 285 Fungus and the Algae, the Fungus extracting water and salts from the substratum and sharing it with the Algae ; but it must be remembered that the Algae are able to flourish, perfectly well without the intervention of the Fungi, while those Fungi which form Lichens are, with few exceptions, FIG. 149. Section through the fruiting part of a Lichen. The stratum of dark rounded bodies (h) represents the algal part of the Lichen; m t the thread-like hyphae of the Fungus constituting the bulk of the body of the Lichen ; s (at the top in one of the sacs), sacs or asci in which the spores of the Fungus are borne. After SACHS. not known to exist without the assistance of the Algae, with which they associate themselves. Figure 148 shows dif- ferent forms of Lichens, and Figure 149 represents a cross section through the body of a Lichen, revealing the tissue formed by the filaments of the Fungus and the embedded Algae. CHAPTER XIII. MOSSES, FERNS, AND HORSETAILS. PROVIDING MATERIALS. Mosses and ferns can be obtained at any time of the year in green- houses. The prothallia of ferns usually grow in great quantities in the shady and moist soil beneath the benches. Mosses may also be found in good condition in the shade and shelter of woods in early spring and summer, and even in the winter season, in some localities. When mosses and fern prothallia are found bearing antheridia and archegonia, it is a good plan to lay in a supply in formalin or 70 % alcohol. Equi- setums, or horsetails, should be gathered in fruiting condition in early spring and summer, and preserved dry or in formalin. Some mosses, ferns, and horsetails should be collected in the fruiting condition and preserved dry for experiments with the spores. OBSERVATIONS. MOSSES. 170. Examine mosses in their natural habitat Separate a single plant carefully from its associates and from the substratum. What is the character of the members which connect it to the substratum ? What is the nature of the substratum ; is it moist or dry ? 171. Examine mosses which are in fruit. The fruiting stage will be recognized as the slender stem growing from the apex of the leafy stem and terminating with a capsule which bears the spores. Examine the spore capsules of different ages. Notice how they normally break open. Examine the opening with a lens, and shake out some of the spores and examine them with a lens. 286 Mosses, Ferns, and Horsetails. 287 172. Examine with a lens the apices of some of the leafy stems which are not bearing capsules. A diligent search is likely to reveal two kinds of structures, very small flask-shaped bodies, termed arcJiegonia, which bear the eggs, and club-shaped bodies, termed antheridia, which contain the sperms. Make drawings of all the members thus far studied. 173. Mount archegonia and antheridia in a drop of water under a coverglass, and examine with medium and high powers. Mount and examine, in the same manner, some of the spores contained in the capsules. Draw as seen with both low and high powers. 174. Boil pieces of soft brick, and, after cooling, place them in a dish of water so that they are but little sub- merged. Scatter the spores over the brick, cover with a bell jar, and set in strong diffuse light, but not in direct sunlight. When delicate green filaments (protonemata, singular protonemd) begin to appear over the brick, scrape off some of them, mount in a drop of water under a cover- glass, and examine with medium and high powers. Leave the brick under the bell jar, replenish the water as needed, and observe developments. 175. Remove a leaf from a moss, mount in a drop of water under a coverglass, and examine with a high power. How many cells thick is the leaf? What is the form of the chloroplasts ? Are stomata present ? Place a drop of chloral hydrate-iodine on the slip in contact with the cover- glass, and draw out the water with a piece of filter paper placed against the opposite edge of the coverglass. As the chloral hydrate-iodine replaces the water, watch the effect upon the chloroplasts. Does starch appear in them ? Do plants which have been kept in the dark give a differ- ent result ? 288 Introduction to Botany. 176. Dig up a clump of mosses in fruit, and place it in a shallow dish containing sufficient water to keep the bottom of the clump moist. Cover it with a bell jar, and after a few hours remove the bell jar and observe the behavior of the capsules as the atmosphere about them becomes less humid. FERNS. 177. Examine ferns in their natural habitat. Note ex- posure to the sun, and the nature of the soil, whether it is moist or dry. Dig up a plant and observe the character of the underground parts. 178. Examine the back of the leaves for the rounded or linear clusters (son, singular sorus) of sporangia. Select a portion of a leaf which shows by the brown color of the sporangia that the spores are ripe, and place it under a bell jar on a piece of moist white filter paper. After a few hours remove the bell jar and examine the paper with a lens to see whether the spores have become scattered. Even old herbarium specimens might answer the purpose. 179. Scatter spores over pieces of brick and keep moist under a bell jar, as directed for the spores of mosses. After a few weeks the spores should have germinated, and the green bodies resulting, known as the prothallia, should be examined under a microscope. How are they anchored to the brick ? After a time archegonia and antheridia should be observable on the under sides of the prothallia. Take care of the experiment until young fern plants begin to grow erect from the prothallia. HORSETAILS. 1 80. Note the character of the habitat in which horse- tails flourish. Dig up some of the plants and observe the nature of the roots and the relation of the plants to each Mosses, Ferns, and Horsetails. 289 other by means of the underground parts. Examine the cylindrical stems. Are there any structures growing from the nodes which may be morphologically leaves ? Halve a stem longitudinally from top to bottom and note its con- struction. 181. Examine the spo- rangia which are borne in cone-like clusters at the tops of the stems. Scatter some of the dry spores on a glass slip and examine with a medium power. Gently breathe on the slip and note the result. Mount some of the spores in a drop of water under a coverglass and examine with a high power. FIG. 150. A, entire moss plant, the leaf-bearing gametophyte with rhizoids, bearing the sporophyte, i.e. the capsule and its stem ; o, the operculum, which falls off and al- lows the spores to escape ; B, the cap- sule surmounted by the calyptra (c); C, capsules with the fringe of teeth open and closed. In part after KERNER. DISCUSSION. MOSSES. 176. Character of Mosses. -The shoot of the moss plant is differentiated into stem and leaves of very simple construction. Filamentous outgrowths, called rhizoids, anchor the plant to the sub- stratum, and have the absorptive function of the roots of the higher plants (Fig. 150). Because of their simple con- struction and lack of an effective protection against too great transpiration, the mosses are mostly restricted to moist and shady situations, although some species occur in exposed localities, having acquired the power of reviv- ing after long periods of desiccation. The leaves of 290 Introduction to Botany. mosses perform the same functions as do those of higher plants. 177. Reproduction of Mosses. An examination of the apices of moss shoots reveals the fact that archegonia and antheridia (Fig. 151) are pro- duced there, in some species both on the same plant, and in others on different plants. The archegonia and anther- idia are small and obscure, and would be overlooked by the casual observer. The wall of the antheridium breaks open at its apex (Fig. 151, B\ and the sperms (s and /) being freed, swim about in the dew or rain which has collected over the plants ; and being attracted by some chem- ical substance secreted within the archegonia (Fig. 151, A) they enter these through their FlG - I 5 I - hollow apical elongations, and A, archegonium with egg cell at the base one sperm in each Case f USCS of the cavity, and B, antheridium of a i -i moss. At j and t are sperms ; these With the egg. are seen escaping from the apex of B. Tn e fertilized egg immedi- All highly magnified. After SACHS. ately germinates without leav- ing its position in the archegonium, and the rod-shaped embryo, as it elongates, breaks off the narrow upper part of the archegonium and carries it as a sort of cap called the calyptra (Fig. 150 B, c). At the same time the lower part of the embryo pushes its way down into the tissues of the parent plant, from which it continues to draw food until Mosses, Ferns, and Horsetails. 291 the time of its maturity ; that is, until the capsule contain- ing the ripened asexual spores has been formed at its apex. The asexual spores are capable of germination as soon as formed, but, instead of producing a leafy moss plant imme- diately, they first form filamentous outgrowths called pro- tonemata, resembling the filamentous Algae (Fig. 152, A and B\ Finally buds (Fig. 152, B) are formed on the protonemata, which develop into the leafy moss plant. FIG. 152. A, germinating moss spore ; B, proionema produced by further development of A. To the left, near the base, is a bud which is to become a moss plant. After SACHS. The life history of a moss exhibits an alternation of two sorts of generations ; the leaf -bearing generation, with its archegonia and antheridia, known as the sexual generation, or gametophyte, and the leafless asexual generation, or sporophyte, namely, the capsule and its stalk, which grows from the fertilized egg in the archegonium and produces spores asexually. It should be observed that the asexual generation in its young state bears chlorophyll, and must therefore be able to manufacture a portion of its food, at least for a time. 178. Dissemination of Spores. It will be seen that after the top, or operculum (Fig. 150, O\ of the sporangium has 292 Introduction to Botany. broken away the spores are still kept from falling out by means of a fringe of teeth (Fig. 150, C) ; these are more or less hygroscopic in different species. They close the opening of the cap- sule in a humid atmosphere and open outward to allow the spores to be shaken out in a dry atmosphere. The winds probably dry the teeth and shake out the spores at the same time. FERNS. FIG. 153. 179. Character of Ferns. An examination of the construction of a fern shows it to be much more Scolopendrium, a fern bearing hi g hl y Organized than a niOSS. The oblong clusters of sporangia tissues of its stem and leaves are (sort, singular sorus} . After -i rr . . . i . r STRASBURGER. differentiated to perform separate functions, as we have seen to be the case in the higher plants, and it has true roots. The leaves not only perform the usual photosynthetic function of green leaves, but they may also bear spores asexually on their under surface (Fig. 153); and since no part of the fern plant bears sperms or eggs, we must look upon it as an asexual genera- r IG. I54 tion, or sporophyte, . J Cross section through a sorus of Scolopendnum. Which in the moSS we a and d, sporangia containing spores (the Saw tO be leafless spore is the unicellular stage of the gam eto- phyte) produced asexually ; c, the protective (namely, the Capsule covering or indusium. After STRASBURGER. Mosses, Ferns, and Horsetails. 293 and stalk bearing it) and more or less parasitic on the sexual generation. 180. Reproduction of Ferns. The sporangia (Fig. 1 54) and the spores contained in them are, in some of the ferns, direct descendants of a single epidermal cell. In other ferns they originate in several cells of the epi- dermis and deeper-lying tissues. When the spores FIG. 156. C, archagonium of a fern with its egg cell ; D, an antheridium with sperm cells ; , an empty anther- idium ; F and G, motile sperms. After STRASBURGER. FIG. 155. F, prothallium orgametophyte of a fern seen on its under surface. The hairs are the rhizoids. At a are archegonia, at b antheridia. G, a prothallium bearing a young fern plant or sporophyte. After STRASBURGER. are ripe, the sporangia break open elastically on imbibing moisture and throw the spores to some distance. When the spores ger- minate, they do not immediately produce the fern plant, but in- stead, a small thin body known as the prothallium (Fig. 155), which lies flat on the substratum. The prothallium, which may be a centimeter or less in diameter, bears qn its under surface eggs in archegonia, and sperms in antheridia (see Fig. 156). The sperms are minute ciliated bodies. They become discharged from the antheridia and swim in the rain water or dew in quest of the egg, being attracted by a 294 Introduction to Botany. substance secreted within the archegonium. After fertiliza- tion, by coalescence with a sperm, the egg begins a series of divisions resulting in the formation of a young fern plant, whose leafy stem turns upward and seeks the light, and whose root turns downward, penetrating the substratum. The prothallium bears the sex organs and constitutes the sexual generation. It contains chlorophyll, and is con- nected with the substratum by absorbing hairs called rhizoids, and is able to sustain an independent existence, in some instances for several years. 181. Comparison of Asexual and Sexual Generations. We note that while the sexual generation is the more con- spicuous in the mosses, it becomes subordinate in size and differentiation in the ferns. In this respect the ferns may be looked upon as intermediate between the mosses, together with other lower plants, and the Spermatophytes or seed-bearing plants. In the Spermatophytes, as in the ferns, the asexual generation is the more highly developed, the sexual generation being reduced to such an extent that it requires good powers of the microscope to demonstrate it ; while the asexual generation is composed of leaf, stem, root, and all of the flower up to a certain stage of its development. These facts can be summarized and compared by refer- ence to the diagrams of Figs. 157, 158, 159. In these figures the sporophyte is unshaded and the gametophyte (after the germination of the spore) shaded. The fern will be considered first, since in it the distinction between sporo- phyte and gametophyte is most evident. When the fern spore (Fig. 157, d) germinates, a multi- cellular body (A) is produced (prothallium) bearing sex organs, namely, archegonia (a), containing each an egg cell, and antheridia (), bearing sperms. Since the pro- Mosses, Ferns, and Horsetails. 295 thallium bears the sex organs, it is rightly called the sexual genera- tion, or gametophyte. The egg, having been fertilized by fusion with a sperm (see paragraph 180), undergoes segmentation ; and the cellular division thus begun con- tinues indefinitely, resulting in a conspicuous fern plant (Fig. 157 B, e) which bears spores asexually. As has been said, the fern plant has no sex organs, and is there- fore called the asexual generation, or sporophyte. During the cell divisions which are immediately concerned in the formation of the spore, the number of the chromosomes entering into the constitution of the nucleus is reduced by one-half (see page 109 for a description of cell and nuclear division), so that the spore con- tains only one-half as many chro- mosomes as do the cells which make up the body of the fern plant, but precisely the same number as the cells of the prothallium or gameto- phyte. Therefore we look upon the spore as the one-celled stage of the gametophyte. When the nucleus of the sperm cell fuses with that of the egg cell, the number of chromosomes now entering into the Diagrams of the sporophyte and gametophyte of a fern. The spore d produced asexually on the fern plant e (sporophyte) is the beginning of the gameto- phyte. All of the gametophyte produced by the germination of the spore is shaded ; all of thesporophyte is left unshaded. A, the prothallium (gameto- phyte) bearing an archego- nium (a) with its egg, and an antheridium (<$)with its sperms. The fern plant e grows from the fertilized egg. B t a later stage than A. 296 Introduction to Botany. constitution of the nucleus of the fertilized egg is doubled by this union, so that the fertilized egg contains the same number of . chromosomes as do the nuclei of the cells which make up the body of the fern plant or sporophyte springing from the fertilized egg. Therefore we look upon the ferti- lized egg as the one-celled stage of the sporophyte. When the moss spore (Fig. 158, ri) germinates, a multicellular body is produced (protonema, /) from which springs the moss plant (g) bearing antheridia (r) and arche- gonia (s) at its summit. Evidently, therefore, the entire body resulting from the germination of the spore is the gametophyte. The egg after fertilization produces the slender stalk (/) and capsule (m), namely, all of the unshaded part of Fig. 158, B, which must be the sporo- phyte, since it is produced in the same manner (namely, from the fertilized egg within the archego- nium) and has the same position in the life cycle as has the fern plant in the life cycle of the fern. It is true that the stalk and capsule appear to be an organic part of -the moss plant, but from the evidence before us we must conclude that FIG. 158. Diagrams of the sporophyte and gametophyte of a moss. The spore n produced asexu- ally in the capsule m (which with its stalk / is the sporo- phyte) is the beginning of the gametophyte. All of the gametophyte produced by the germination of the spore is shaded ; all of the sporo- phyte is left unshaded, p in A, the protonema from which springs the moss plant g (gametophyte together with /) , bearing an archegonium (s) with its egg, and an an- ther idium(r) with its sperms. B, a later stage, the capsule or sporophyte having sprung from the fertilized egg. Mosses, Ferns, and Horsetails. 297 they are neither more nor less than the sporophyte parasitic upon the gametophyte. We see that in pro- ceeding from the moss to the fern, or from a lower to a higher type of vegetation, the ga- metophyte becomes much reduced in size and complexity of structure, while the sporophyte relatively advances in these re- spects (compare shaded and unshaded portions of Figs. 157-158). Turning now to the Spermatophy tes or flow- ering plants, the most complex and special- ized of plants, and the latest product of plant evolution, we find two kinds of spores (read paragraph 142, page 201), the pollen spores and the embryo sac spore within the ovule. The fact that the em- bryo sac is a spore is not so evident from its appearance as from its behavior. In tracing the life cycle of a fern and a moss we began with the germination of the spores, and we shall begin at FIG. 159. Diagrams of the sporophyte and gametophytes of a flowering plant. The pollen spore (d) produced asexually on the plant (sporophyte) is the beginning of the male gametophyte, and the embryo sac spore m, also produced asexu- ally on the sporophyte, is the beginning of the female gametophyte. All of both gameto- phytes (e and n) produced by the germination of both kinds of spores is shaded ; all of the sporophyte is left unshaded. There is no dif- ferentiated archegonium and antheridium on the gametophytes. b and c, later stages than a. The young sporophyte or embryo (0) has sprung from the fertilized egg. At/ is the endosperm. 298 Introduction to Botany. the same place in the life cycle of a flowering plant. The pollen spore consists of a single cell (Fig. 159, d\ as does the spore of a moss or fern. We find, however, that after a time, and even before it is discharged from the anther, the pollen spore has become two-celled (e). The germina- tion of the spore of a moss or fern began by the division of its single cell, one cell becoming two, two becoming four, etc., until the complete gametophyte is formed ; and we may conclude from this that the division of the pollen spore is the beginning of its germination and of the formation of the complete gametophyte. Following the further behavior of the pollen, as described on page 166, we find that after it has been transferred to the stigma its inner wall forms a tube penetrating to the ovule, and that one of its two cells passes through the tube to the ovule, having first divided, or subsequently dividing, to form two cells, one of which fuses with and fertilizes the egg cell, and for that reason must be considered a sperm. From this we are led to the conclusion that the three cells result- ing from the germination of the pollen spore constitute a gametophyte. The great elongation of the inner wall of the pollen spore producing the pollen tube does not have its counterpart in the germinating spores of ferns and mosses. The pollen tube functions in part as an anther- idium, although being apparently not its homologue. The behavior of the embryo sac spore will now be traced. It is a single large cell (m) which never becomes discharged from the place of its formation within the ovule. Usually before the descent of the pollen tube its nucleus divides and the daughter nuclei continue the process of division until eight nuclei have been formed, four of them taking position at the micropylar and four at the opposite end of the embryo sac (n). One from each Mosses, Ferns, and Horsetails. 299 of these groups then moves toward the center of the embryo sac (see Fig. 88), and the two fuse, forming one, which by repeated division gives rise to the endosperm tissue of the seed. A plasma membrane is organized about each of the remaining nuclei of the two groups, including with each some of the cytoplasm of the embryo sac, thus forming definite cells. When a sperm cell leaves the pollen tube, it is found to penetrate and fuse with one of the three cells at the micropylar end, resulting in its fertilization and subsequent division and ultimate forma- tion of the embryo (E, page 38. Pistils 2-5, somewhat united at the bases of the ovaries; trees or shrubs. SAPINDACE^E, page 74. Pistil i and simple, with i parietal placenta, or sometimes 2-celled, with a row of ovules in each cell. LEGUMINOS.E, page 65. Pistil i, compound, as shown by the number of cells, placentae, styles, or stigmas. Ovary i-celled. Corolla irregular; petals 4, somewhat united; stamens 6, and diadelphous. FUMARIACE.E, page 46. Corolla irregular; petals and stamens 5; placentae 3, parietal. VIOLACE.E, page 79. Corolla nearly or quite regular. Ovule i ; styles or stigmas 1-3. Shrubs or trees. ANACARDIACE,E, page 73. Ovules more than i on a central or basal placenta; herbs with tumid nodes. CARYOPHYLLACE.E, page 37. Ovary 2 or more celled. Flowers irregular; ovary 3-celled. SAPINDACE^E, page 74. Flowers nearly or quite regular. Stamens tetradynamous (sometimes fewer than 6) ; petals 4. CRUCIFER^E, page 47. io Introduction to Botany. Stamens io (rarely only 5), somewhat monadelphous at base, leaves 3-foliate, or more or less lobed and divided. GERANIACE^, page 70. Stamens 5, carpels 3, pod inflated. SAPINDACE/E, page 74. (3) Ovary inferior, being more or less adherent to the calyx. Ovary i-celled, many-seeded; 2 parietal placentae. SAXIFRAGACE^E, page 54. Ovary 4-celled (sometimes 2-celled) ; pollen cobwebby. ONAGRACE^E, page 81. Ovary 2-5-celled ; petals 5; fruit a 2-several-celled pome; shrubs or trees. ROSACE^E, page 56. Ovary 2-celled ; style i; ovule i in each cell; petals 4; fruit a 2-seeded drupe. CORNACE^, page 86. Ovary 2-celled; styles 2; i ovule in each cell; petals 5. UMBELLIFER^E, page 82. C. Corolla and calyx present, the petals more or less united (gamopetalous). (1) Stamens more numerous than the corolla lobes. Pistil i. Ovary i-celled, with i parietal placenta. LEGUMINOS^E, page 65. Ovary 3~i2-celled. Stamens free from the corolla, or nearly so. ERICACEAE, page 86. Stamens borne on the base of the corolla. EBENACE^E, page 90. Ovary 5-celled; stamens monadelphous at base. GERANIACE^, page 70. Pistils several, their ovaries united in a ring; the numerous stamens monadelphous. MALVACEAE, page 78. (2) Stamens as many as the lobes of the corolla, and opposite them. Ovary i-celled, several-seeded; style i. PRIMULACE^E, page 88. (3) Stamens of the same number as the corolla lobes (or fewer), and alternate with them, (a) Ovary inferior, being surmounted by the other parts. Stamens united by their anthers into a ring; flowers in an involucrate head. COMPOSITVE, page 116. Stamens separate, and free from the corolla, or nearly so. CAMPANULACE^:, page 115. Stamens inserted separately on the corolla. Ovary 3-celled. Stamens 1-4. VALERIANACE^E, page 114. Ovary 2-5-celled. Leaves opposite, with stipules, or in whorls. RUBIACE^E, page no. Leaves opposite, without true stipules. CAPRIFOLIACE^E, page 112. (3) Ovary superior, or free from the other parts. Corolla irregular. Ovary 4-lobed, with i central style ; corolla labiate. LABIAT/E, page 99. Ovary 4-celled, but not lobed, with terminal style; corolla somewhat 2-lipped. VERBENACE/E, page 98. Ovary i-celled, with free central placenta. Calyx and corolla 2-lipped. Aquatic herbs. LENTIIULARIACE^:, page 105. Ovary i-celled, with 2 or 4 parietal placenta;; corolla more or less 2-lipped. OROBANCHACE^:, page 106. Key. ii Ovary and pod 2-celled by the meeting of 2 parietal placentae. Calyx and corolla more or less 2-lipped. Trees or woody climbers. BIGNONIACE. verna, L. (L., verna, a native.) VERNAL WHITLOW GRASS. Flowers white ; petals deeply 2-cleft. I to 5 inches high ; flowering stems leafless. Leaves tufted at the base, oblong or spatulate-oblanceolate, entire or only dentate, beset with stiff, stellate hairs. Pods oblong or oval, smooth, shorter than the pedicels. In fields and sandy waste places. 2. Draba Caroliniana, Walt. CAROLINA WHITLOW GRASS. Flowers white ; petals entire. Pods linear, longer than the ascending pedicels. Flowering stems i to 5 inches high. Leaves obovate and entire, clustered at the base, or only a short distance up the stem, beset with stellate pubescence. 3. Draba cuneifolia, Nutt. (L., cuneus, wedge ; folium, leaf.) Flowers white ; petals emarginate ; pods oblong-linear, minutely hairy, longer than the horizontal pedicels. 4 to 8 inches high, branching and leafy below; leaves obovate, cuneate, or the lowest spatulate, dentate toward the summit. In fields and grassy places. 4. Draba brachycarpa, Nutt. (Gr., brachys, short; karpos, fruit.) SHORT- FRUITED WHITLOW GRASS. Flowers yellow ; the oblong pods & to inch long. Basal leaves \ to 5 inch long, ovate or obovate, stem leaves oblong and entire. Dry hills and fields. ARABIS. RockCress. (Named from Arabia.) Flowers white or purple. Pods linear, elongated, and flattened par- allel with the partition; valves mostly i-nerved. Seeds in i or 2 rows in each cell, usually margined or winged. Leaves seldom divided. 1. Arabis Ludoviciana, Meyer. Stems ascending from 5 to i foot high. Stem leaves pinnatifid, oblong, and narrow. Flowers very small and white. Pods linear, spreading, nearly i inch long; seeds as broad as the pod, and winged. In open places. 2. Arabis dentata, T. & G. TOOTHED ROCK CRESS. Petals greenish white, hardly exceeding the calyx; pods narrowly linear, sometimes exceeding i inch' in length. Seeds oblong, in i row in each cell. Stems sparingly branched, i to 2 feet high. Basal leaves obovate and dentate, on margined petioles; stem leaves oblong or oblanceolate, dentate, sessile, base auricled and clasping. XIV. ALYSSUM. (Gr., a, without or depriving; lyssa, madness. Greek name of a plant supposed to have remedial value.) Flowers white (or sometimes yellow). Pods orbicular, flattened at the margins parallel with the partition ; seeds only i or 2 in each cell. 54 Introduction to Botany. i. Alyssum maritimum, L. (L., maritimus, relating to the sea.) SWEET ALYSSUM. White, honey-scented flowers. Stems spreading ; leaves lanceolate or linear, entire, green, or slightly hoary. Rounded pods with a single seed in each cell. Cultivated. SAXIFRAGACE^. SAXIFRAGE FAMILY. Herbs or shrubs with opposite or alternate, exstipulate leaves. Flowers perfect or polygamo-dicecious. Calyx mostly 5-lobed or parted, usually persistent and more or less adnate to the ovary or free from it. Petals 4-5. Stamens sometimes twice as many as the petals (sometimes more numerous), when of the same number alternate with them, perigynous or epigynous. Carpels i-several, mostly 2, united or free. Styles as many as the carpels or cells of the ovary, or united into i. Fruit a capsule, follicle, or berry; seeds mostly many. I. SAXIFRAGA. Saxifrage. (L., saxum, a rock; fran-gere, to break.) Perennial herbs. Calyx 5-lobed, free from or adnate to the base of the ovary. Petals 5 and perigynous. Stamens 10, inserted with the petals. Ovary 2-lobed and 2-celled. Capsule 2-beaked. Seeds numerous. 1. Saxifraga Pennsylvanica, L. SWAMP SAXIFRAGE. Stout, i to 3 or more feet high. Leaves 4 to 10 inches long and sometimes 3 inches wide, varying from oval to oblanceolate, narrowing at the base into a short petiole, clustered at the base. Stem scapose, bearing flowers in large, oblong, open panicles. Calyx reflexed. Petals longer than the calyx, greenish. Follicles divergent when mature. On wet banks or in bogs. 2. Saxifrage Virginiensis, Michx. EARLY SAXIFRAGE. Scapes 4 to 12 inches high, viscid-pubescent. Leaves obovate-spatulate, narrowing into a petiole, crenate or dentate, i to 3 inches long, or longer. Flowers clustered in cymes, the inflores- cence becoming a loose panicle. Flowers white, to J inch broad. Calyx lobes erect, shorter than the petals. Carpels nearly separate and becoming widely divergent in fruit. Dry hillsides and rocky woodlands. II. PHILADELPHIA. Mock Orange or Syringa. (Gr.,#7u70s, loving; adelphos, brother. No obvious reason for the name.) Shrubs with opposite, petioled, exstipulate leaves. Flowers large, white or cream-colored, terminal or axillary. Calyx tube coherent with the ovary, 4~5-lobed. Petals 4-5, rounded or obovate. Stamens 20-40. Ovary 3-5 -celled; styles 3-5, distinct or united. Capsule top-shaped, Dicotyledones. 55 dehiscing loculicidally. The common name syringa is the proper generic name for the lilac. i. Philadelphia coronarius, L. (L., coron&rius, pertaining to a wreath.) GARDEN SYRINGA or MOCK ORANGE. A shrub 8 to 10 feet high. Leaves 2 to 4 inches long, elliptic or ovate-elliptic, pubescent beneath, denticulate. Flowers racemose at the ends of the branches, an inch or more broad, creamy white and fragrant. Cultivated ; escaped from gardens in some localities. m. RIBES. Gooseberry and Currant. (Ar., ribes, gooseberry.) Shrubs with alternate and often fascicled, lobed leaves. Calyx 5- lobed, the tube coherent with the ovary. Petals 5 and small, inserted at the throat of the calyx. Stamens 5, alternate with the petals. Ovary i -celled, with 2 parietal placentae. Styles 2, distinct or united. Fruit a pulpy, globose, or ovoid berry, bearing the remains of the calyx at its summit. 1. Ribes Cynosbati, L. (Gr., tynosbatos, the dog-thorn.) WILD GOOSEBERRY or DOGBERRY. Flowers 1-3. Calyx tube ovoid-campanulate, green. Berry beset with awl-shaped prickles. In rocky woods. 2. Ribes setosum, Lindl. (L., setosus, bristly.) BRISTLY GOOSEBERRY. Flowers 1-4, calyx tubular and white. Stem with numerous prickles. Fruit glabrous or only sparingly prickly. In thickets and along lake shores. 3. Ribes gracile, Michx. (L., gracilis, slender.) MISSOURI GOOSEBERRY. Flowers about 3, white or greenish, drooping. Lobes of the calyx longer than the tube. Stamens much exserted. Berry reddish purple. In rocky or dry soil. 4. Ribes oxycanthoides, L. (Gr., oxys, sharp ; akanthos, spine ; eidos, resem- blance.) HAWTHORN or NORTHERN GOOSEBERRY. Flowers 1-3 on short pedi- cels, greenish purple or white. Stamens short, not exserted. Stems scarcely prickly. Fruit reddish purple when ripe, smooth. In low grounds or damp woods. 5. Ribes floridum, L'Her. (L., floridus, flowery.) WILD BLACK CURRANT. Leaves somewhat pubescent and resinous-dotted beneath. Flowers many in pendulous racemes, greenish white. Calyx tube cylindric. Fruit smooth, black, and globose-ovoid when ripe. In woods. 6. Ribes rubrum, L. (L., ruber, red.) RED CURRANT. Without prickles. Leaves 3~5-lobed and serrate. Flowers in loose, pendulous racemes, greenish or purplish. Calyx tube campanulate. Stamens short. Fruit red and smooth. 7. Ribes cereum, Dougl. (L., cereus, waxy.) WHITE-FLOWERED or SQUAW CURRANT. Flowers sessile or on short pedicels in short racemes, from the same buds as the rounded, reniform leaves, whitish or greenish white. Calyx tube tubular and glandular. Fruit red and insipid. 8. Ribes aureum, Pursh. (L., aureus, golden yellow.) GOLDEN, BUFFALO, 56 Introduction to Botany. or MISSOURI CURRANT. Flowers several in leafy-bracted racemes, yellow, spicy- scented, ^ to i inch long. Calyx tube cylindric, about 3 times as long as the lobes. Fruit smooth, yellow, becoming black. Along streams. ROSACES. ROSE FAMILY. Herbs, trees, or shrubs with alternate, mostly stipulate, leaves. Flowers regular ; sepals 5, often subtended by as many sepal-like bractlets ; petals 5, apparently inserted on the calyx ; stamens usually indefinite, apparently inserted on the calyx (expanded border of the base of the receptacle). Pistils i-many, distinct or united. Some of our most beautiful flowers and best fruits belong to this family. Longitudinal diagrams of type flowers of the Rosaceae. A t plum; B, rose ; C, strawberry. Ovary superior or half superior. Ripened pistil a drupe or drupelet. Fruit consisting of a single pistil. PRUNUS I. Fruit consisting of several pistils cohering over an elongated receptacle. RUBUS IV. Ripened pistil a few- to several-seeded pod. Pistils 5-8; pods not inflated. SPIRAEA II. Pistils 1-5; pods inflated. PHYSOCARPUS III. Ripened pistil an achene. Carpels distinct and numerous on a convex receptacle, which becomes fleshy and edible in fruit. FRAGARIA V. Carpels distinct on a dry feceptacle; styles not lengthening in fruit; bracts conspicuous at the sinuses of the calyx. POTENTILLA VI. Carpels 2-6 on a short receptacle; styles not lengthening in fruit; bracts at the sinuses of the calyx minute or wanting. WALDSTEINIA VII. Carpels numerous on a dry conical or cylindrical receptacle; style persisting as a hairy or jointed tail to the achene. GEUM VIII. Ovary inferior. Pistils several, inclosed in an urn-shaped receptacle. ROSA IX. Pistil single, compound, its cells as many as the styles (2-5). Fruit a pome; ovary s-celled, its carpels 2-seeded. PVRUS X. Fruit a small, berrylike pome; ovary becoming lo-celled, its carpels 2-seeded. AMELANCHIER XI. Fruit a small, drupelike pome with 1-5 bony stones. CRATVEGUS XII. Dicotyledones. 57 I. PRUNUS. Plum, Cherry, Peach. (The ancient Latin name.) Trees or shrubs, with leaves mostly simple and serrate. Flowers perfect ; lobes of calyx and corolla 5 ; ovary superior and free from the so-called calyx tube at maturity. Stamens 15-20; pistil i, with 2 pendulous ovules. Fruit a fleshy drupe with a hard stone. 1. Prunus Americana, Marsh. WILD YELLOW or RED PLUM. Flowers in lateral umbels, white, appearing before the leaves, about i inch broad. Calyx lobes entire and pubescent within. Leaves ovate or obovate-acuminate, nearly glabrous when mature. Branches somewhat thorny. Fruit red or yellow, globose, little or no bloom ; stone slightly flattened. Shrubs or small trees. River banks and woods. 2. Prunus Watsoni, Sargent. (Latin genitive of proper name.) SAND PLUM. A somewhat spiny shrub, 6 to 10 feet high. Flowers in numerous lateral fascicles, about 5 inch in diameter. Leaves ovate to ovate-lanceolate, finely serrulate, shining above. Petals oblong-obovate and short-clawed. Globose fruit about f inch in diameter, no bloom, flesh yellow. In sandy soil. 3. Prunus Chicasa, Michx. (Latinized form of Chickasaw, Indian name.) CHICKASAW PLUM. A small tree with somewhat thorny branches. Flowers in lateral umbels, expanding shortly before or with the leaves. Leaves lanceolate or oblong-lanceolate, serrulate, glabrous when mature. Drupe red, 5 to | inch in diameter; bloom scant; skin thin; stone ovoid, hardly flattened. In dry soil. 4. Prunus Besseyi, Bailey. (Latin genitive of proper name.) WESTERN SAND CHERRY. A shrub, i to 4 feet high. Flowers in lateral umbels, expanding with the leaves, \ to nearly \ inch in diameter. Leaves mostly elliptic or oblong- elliptic. Stipules of young shoots often longer than the short petioles. Fruit black, mottled, or yellow, 5 to inch in diameter, astringent. Branches often spreading and prostrate. Prairies. 5. Prunus Persica, Sieb. & Luce. (L., persicus, persian.) PEACH. Small trees. Leaves thin, lanceolate, serrate. Fruit large and edible ; stone thick-walled, somewhat compressed, deeply wrinkled. Flowers pink, about inch in diameter; borne in clusters. 6. Prunus Pennsylvania, L. f. WILD RED CHERRY. Small tree. Flowers on long pedicels, many in a corymbose cluster. Leaves oval or lanceolate on slender petioles, shining on both sides, serrulate, unfolding with the flowers. Fruit small and globose, with thin skin and sour flesh, light red. Stone globular. In rocky woods. 7. Prunus Virginiana, L. CHOKE CHERRY. A shrub 2 to 10 feet high. Flowers in racemes, terminating shoots of the season. Leaves obovate or broadly oval, sharply serrulate with slender teeth. Drupe red or nearly black, about J inch in diameter, very astringent. Stone globular. Along river banks. 58 Introduction to Botany. 8. Prunus serbtina, Ehrh. (L., serotinus, late ripe.) WILD BLACK CHERRY. Large tree. Flowers in racemes, terminating leafy branches. Leaves thick, oval to oval-lanceolate. Drupe dark purple or black, about \ inch in diameter, some- what astringent, but sweetish and pleasant. In woods. n. SPIRffiA. Meadowsweet. (Gr., speirao, to twist; from the spiral pods of some species.) Shrubs or perennial herbs, with simple, pinnatifid, or pinnate leaves and white or rose-colored flowers in corymbs and panicles. Calyx 5-cleft, short, and campanulate. Petals 5, inserted on the calyx. Stamens 10-60. Pods 5-8, not inflated, few to several-seeded. 1. Spiraea corymbosa, Raf. (Gr., korym'bos, a cluster.) CORYMBED SPIRAEA. Shrub, i to 3 feet high. Leaves oval to orbicular, unequally and coarsely serrate from some distance above the base, thick. Flowers in terminal corymbs, white, about $ inch broad. Pods glabrous. Mountains and rocky places. 2. Spiraea salicifolia, L. (L., salix, willow ; folium, leaf.) WILLOW-LEAVED or COMMON MEADOWSWEET. An erect shrub, 2 to 4 feet high. Leaves oval, obovate, or oblanceolate, sharply serrate above the middle; nearly glabrous throughout. Flowers in dense terminal panicles. Flowers white or tinged with pink, about J to inch broad. In swamps or moist grounds. 3. Spiraea lobata, Jacq. (Gr., lobos, a lobe.) QUEEN OF THE PRAIRIE. Perennial herb, -2 to 8 feet tall. Leaves interruptedly 3~7-foliate ; leaflets 3~5-lobed or parted and unequally serrate or incised ; terminal leaflet y-o-parted ; the lower leaves sometimes 3 feet long. Stipules persistent and serrate. Flowers pink or purple, fragrant, borne in a panicle on a long, naked peduncle. Pods 5-8 i-2-seeded. Moist ground and prairies. 4. Spiraea Ariincus, L. (L., aruncus, beard of a goat.) GOAT'S BEARD. Smooth, tall, perennial herb with 2-3-pinnate, large leaves on long petioles; leaflets ovate to lanceolate, sharply doubly serrate. Flowers small, whitish, and dioecious in panicled, slender spikes. Pods 3-5, several-seeded, pedicels reflexed in fruit. In rich woods. III. PHYSOCARPUS. Nine-bark. (Gr.,physa, a bladder; karpos, fruit.) Branching shrubs with palmately lobed leaves, and white flowers in umbel-like corymbs. Carpels 1-5, inflated; stamens 30-40. In other respects like Spircea. i. Physocarpus opulifolius, Maxim. (L., opulus, a kind of maple; folium, leaf.) NINE-BARK. Shrub, 3 to 10 feet high with recurved branches, the bark peeling off in thin strips. Leaves petioled, ovate-orbicular, 3-lobed, serrate, i to 2 inches long, or longer on young shoots. Corymbs terminal, peduncled, nearly Dicotyledones. 59 spherical, many-flowered, i to 2 inches across. Flowers white or purplish. Pods purplish and conspicuous. River banks and rocky places. IV. RUBUS. Bramble. Raspberry. Blackberry. (The Roman name, allied to L., ruber, red.) Herbs, shrubs, or trailing vines. Calyx without bractlets, 5-parted. Petals 5 ; stamens numerous. Carpels several, seldom few, on a convex or elongate receptacle, ripening into drupelets and forming an aggregate fruit. Flowers usually white, sometimes pink or purple, and fruit edible. 1. Rubus strigosus, Michx. (L., strigosus, lean or thin.) WILD RED RASP- BERRY. Biennial shrubby stems, 3 to 6 feet high, densely covered with weak, glandular bristles, or hooked prickles on the older stems. Leaves 3-5-foliate, leaflets ovate or ovate-oblong. Inflorescence both terminal and axillary. Flowers white, 3 to 5 inch broad ; petals and sepals about equal, both spreading. Fruit light red, elongate-hemispheric. Hills and thickets. 2. Rubus occidentalis, L. (L., occidentalis, western.) BLACK RASPBERRY. THIMBLEBERRY. Stems canelike and recurved, sometimes as much as 12 feet long, decidedly glaucous, and sparingly beset with small, hooked prickles. Leaves mostly 3-foliate, serrate, and somewhat incised, white-pubescent beneath. Inflores- cence usually terminal, compact-corymbose. Fruit purple black, hemispheric. 3. Rubus triflorus, Richardson. (L., fri, three ; fas, floris, flower.) DWARF RASPBERRY. Stems 6 to 18 inches long, trailing or ascending, somewhat pubescent, and without prickles. Leaves pedately or pinnately 3-foliate, sometimes 5-foliate. Flowers 1-3 on slender, glandular-pubescent peduncles; sepals reflexed. Fruit red purple. Swamps or wooded hillsides. 4. Rubus hispidus, L. (L., hispidus, bristly.) RUNNING SWAMP BLACK- BERRY. Stems slender and creeping, slightly woody, beset with weak bristles; erect or ascending branches, 4 to 12 inches long, with few or no prickles. Leaves of 3, rarely 5 obovate, obtuse, unevenly serrate leaflets. Flowers racemose and axillary or terminal, 5 to inch in diameter. Fruit composed of a few drupelets, small, black, and sour, remaining on the receptacle. In low woods or swamps. 5. Rubus trivialis, Michx. (L,., trivialis, common.) LOW-BUSH BLACKBERRY. Stems several feet long, trailing or procumbent, bristly and prickly. Leaves mostly 3-foliate, coriacious and evergreen, nearly or quite glabrous. Peduncles prickly, i-3-flowered. Flowers about i inch broad. Sepals reflexed, much shorter than the petals. Fruit black, sometimes i inch long, pleasant, remaining on the receptacle. In sandy soil. 6. Rubus Canadensis, L. LOW-RUNNING BLACKBERRY or DEWBERRY. Stems shrubby, becoming several feet long, and trailing, naked or with scattered prickles. Leaves 3-y-foliate, leaflets ovate to ovate-lanceolate. Flowers few, termi- nal, and racemose or solitary; peduncles leafy. Fruit delicious, sometimes i inch long, remaining on the receptacle. In dry soil. 60 Introduction to Botany. V. FRAGARIA. Strawberry. (L.,fraga, strawberry.) Acaulescent, perennial herbs, propagating by runners. Leaves 3-foliate, basal, and tufted, on long petioles with a sheathing mem- branous stipule. Flowers on erect, naked scapes, corymbose or racemose, polygamo-dioecious. Sepals 5-bracteolate, persistent, deeply 5-lobed. Petals 5, obovate, clawed, white. Stamens numerous. Car- pels numerous, on an elongated receptacle which becomes fleshy and edible in fruit ; carpels becoming dry achenes. 1. Fragaria Virginiana, Duchesne. VIRGINIA or SCARLET STRAWBERRY. Leaflets thick, broadly oval or obovate ; petioles 2 to 6 inches long ; inclined to be villous-pubescent with spreading or appressed hairs. Fruit ovoid, red, the achenes imbedded in pits. Scape shorter than the leaves. In fields or woodlands. 2. Fragaria vesca, L. (L.,vescas, small or thin.) EUROPEAN WOOD STRAW- BERRY. Leaflets thick, broadly oval or ovate, usually not so villous as the pre- ceding. Scapes longer than the leaves, and the fruit lifted above them. Fruit hemispheric or conic, red, achenes not imbedded in pits. Fields and rocky places. VI. POTENTILLA. Cinquef oil or Five-finger. (L. , potens , powerful, from reputed medicinal value of one of the species.) Herbs, rarely shrubs. Leaves digitately or pinnately compound, alternate, stipulate. Flowers perfect, cymose or solitary. Calyx usually 5-lobed, subtended by as many bractlets. Petals mostly 5, often emar- ginate, yellow, white, or purple. Stamens usually many, sometimes 5-10. Carpels numerous, on a dry receptacle which is often hairy. 1. Potentilla arguta, Pursh. (L., argutus, sharp, pungent.) TALL or GLANDU- LAR ClNQUEFOlL. Flowers white, cymose. Stout and erect, i to 4 feet high. Basal leaves with 7-11 leaflets, long-petioled. Stem leaves shorter with fewer leaflets. Leaflets cut-serrate. Flowers white, about ? inch broad, in terminal cymes. Plant glandular-pubescent. 2. Potentilla argentea, L. (L., argenteus, silvery.) SILVERY or HOARY ClNQUEFOlL. Flowers yellow, cymose. Stems ascending, tufted, 4 to 12 inches long, white from woolly pubescence. Leaves digitately 5-foliate, the divisions lanciniate beyond the middle, green above, white beneath. In dry soil. 3. Potentilla Norvegica, L. ROUGH CINQUEFOIL. Flowers yellow in termi- nal cymes. Erect and stout annuals or biennials with rough pubescence, 6 inches to 2 feet or more high. Leaves 3-foliate, the lower petioled, upper stem leaves nearly or quite sessile. Leaflets obovate to oblong-lanceolate. Styles glandular- thickened at the base. In dry soil. 4. Potentilla leucocarpa, Rydberg. (Gr., leukos, white ; karpos, fruit.) DIP- Dicotyledones. 61 FUSE CiNQUEFOlL. Flowers yellow in loose, leafy cymes. Diffuse, rather weak annual, 6 inches to 3 feet high. Leaves, all but the uppermost, 3-foliate and peti- oled. Leaflets thin, oblong, incisely serrate. Styles thickened below. In damp soil. 5. Potentilla Anserina, L. (L., anserinus, pertaining to geese.) SILVER- WEED. Flowers yellow, solitary and axillary. Herbaceous and tufted, spreading by slender runners. Leaves pinnate; leaflets 7-25, oblong to obovate, serrate, white-pubescent beneath. Style filiform. River banks, lake borders, etc. 6. Potentilla Canadensis, L. COMMON CINQUEFOIL or FIVE-FINGER. Flowers yellow, solitary and axillary. Stems tufted, and spreading by slender runners. Leaves digitately 5-foliate, sometimes 3-4-foliate, petioled. In dry soil. VH. WALDSTEINIA. (Named for Francis von Waldstein.) Perennial herbs resembling the strawberry, but with yellow flowers and 2-6 carpels inserted on a short receptacle. Flowers corymbose on bracted scapes. Petals conspicuous and stamens numerous. i, Waldsteinia fragarioides, Tratt. (L.,/raga, strawberries ; Gr., eidos, resem- blance.) BARREN OR DRY STRAWBERRY. Leaves on long petioles, tufted, mostly 3-foliate; leaflets obovate-cuneate, dentate, crenate, or incised. Scapes corymbosely 3-8-flowered; pedicels slender and sometimes drooping. Wooded hillsides. VHI. GEUM. Avens. (Ancient Latin name.) Perennial herbs, with pinnatifid or odd pinnate, stipulate leaves ; basal leaves clustered, stem leaves smaller. Calyx somewhat campanu- late, 5-lobed, usually with 5 bractlets at the sinuses. Petals 5, exceed- ing the calyx. Stamens many, inserted on the disk below the calyx. Carpels many, on an elevated, dry receptacle. Styles persisting in the form of hairy, naked, or jointed tails to the achenes. 1. Geum rivale, L. (L., rivalis, belonging to a brook.) PURPLE or WATER AVENS. Flowers purple and nodding, calyx lobes erect or spreading. Erect, i to 3 feet high, pubescent. Basal leaves lyrately, interruptedly pinnate; stem leaves 3-lobed or 3-pinnate. Achenes very pubescent ; style jointed, and plumose below. In wet meadows and swamps. 2. Geum ciliatum, Pursh. (L., cilium, an eyelash.) LONG-PLUMED PURPLE AVENS. Flowers light purple ; styles very long and plumose throughout. Scapose, pubescent herbs, 6 to 18 inches tall. Scapes 3-8-flowered. Basal leaves tufted, pinnate, leaflets very numerous and cut-toothed. In rocky soil. 3. Geum album, Gmel. (L., albus, white.) WHITE AVENS. Flowers white, less or more than 5 inch broad. Plants softly pubescent or nearly glabrous, 15 to 62 . Introduction to Botany. z\ feet high. Basal leaves 3-foliate or pinnately divided, the terminal lobe larger and broadly ovate. Stem leaves 3~5-lobed or divided, nearly or quite sessile. Receptacle densely bristly, and styles glabrous, or pubescent below. In shady places. 4. Geum Virginianum, L. ROUGH AVENS. Resembling the preceding species, but stouter and bristly pubescent. Flowers creamy white. Receptacle glabrous or merely downy. Low grounds and borders of woods. 5. Geum macrophyllum, Willd. (Gr., makros, large ; phyllon, leaf.) LARGE- LEAVED AVENS. Flowers yellow. Basal leaves lyrate-pinnate, the terminal lobe much exceeding the others. Lateral lobes 3-6, with smaller lobes interspersed. Upper leaves of 2-4 leaflets. Receptacle glabrous; style slender and jointed, pubescent below. Stems erect and bristly-pubescent. IX. ROSA. Rose. (L., rosa, rose.) Erect or climbing, generally prickly, shrubs. Flowers showy, red, pink, or white, rarely yellow. Lobes of the calyx usually 5 ; petals 5 ; stamens many, all borne around the margin of an urn-shaped receptacle, in which are inclosed numerous carpels, arising from the base. Fruit berrylike, consisting of the thickened, hollow receptacle and inclosed carpels. 1. Rosa setigera, Michx. (L., seta, bristle; gerere, to bear.) CLIMBING or PRAIRIE ROSE. Stems climbing, becoming several feet long, beset with stout, scattered prickles. Leaflets commonly 3, sometimes 5. Stipules very narrow. Styles cohering in a column. Fruit globular and somewhat glandular. Prairies and thickets. 2. Rosa blanda, Ait. (L., blandus, of a smooth tongue, agreeable.) SMOOTH or MEADOW ROSE. Erect, 2 to 4 feet tall, almost destitute of prickles. Leaflets 5-7; stipules rather broad. Styles separate, fruit globose or pyriform, nearly or quite glabrous, tipped by the persistent, long, erect, or spreading sepals. In moist and rocky places. 3. Rosa Arkansana, Porter. ARKANSAS ROSE. Erect, i to 2 feet high, the stems beset with slender bristles. Leaflets 711. Lanceolate sepals persistent, spreading, or reflexed. Fruit globose and glabrous. Prairies. 4. Rosa Woodsii, Lindl. (Latin genitive of proper name.) WOODS' ROSE. i to 3 feet high. Straight spines on the stems, at least below. Leaflets 5-9. Acuminate, lanceolate sepals erect on the globose fruit. Usually with spines just below the stipules. Prairies. 5. Rosa humilis, Marsh. (L., kumilis, low.) Low or PASTURE ROSE. From i to 6 feet high, bushy. Leaflets mostly 5, sometimes 7 ; straight spines below the stipules. Flowers solitary or few together. Sepals deciduous, spreading, com- monly lobed. In dry and rocky soil. Dicotyledones. 63 X. PYRUS. Pear and Apple. (L.,/z>wj, a pear tree.) Trees or shrubs, with conspicuous flowers in corymbed cymes. Receptacle (in this instance commonly called the calyx tube) urn- shaped, fleshy, and adherent to the carpels. Sepals, or lobes of the calyx, 5 ; petals 5 ; stamens numerous. Styles 2-5 ; carpels 2-5, their walls of cartilaginous texture, ovules 2 in each cavity. Fruit, v a pome or berrylike. 1. Pyrus communis, L. (L., communis, common.) COMMON PEAR. Bark smooth, branches apt to have somewhat thorny spurs. Leaves ovate with small teeth. Flowers pure white. Fruit tapering toward the base ; flesh containing grit cells. Native of Europe and Asia. 2. Pyrus Malus, L. (L., malum, an apple.) COMMON APPLE. Trees with spreading branches. Leaves broadly ovate or oval, rounded, or subcordate at the base. Flowers pink or white; calyx tomentose. Fruit 15 to 3 inches in diameter. Native of Europe and Western Asia. 3. Pyrus coronaria, L. (L., coronarius, pertaining to a wreath or crown.) AMERICAN CRAB APPLE. A small tree. Leaves ovate to triangular-ovate, sharply serrate, and frequently somewhat lobed, rounded or somewhat cordate at the base. Flowers rose-colored and very fragrant. Styles woolly and united below. Fruit very acid, greenish yellow, fragrant. In thickets. 4. Pyrus angustifdlia, Ait. (L., angustus, narrow ; folium, leaf.) NARROW- LEAVED CRAB APPLE. A small tree. Leares oval to oblong-lanceolate, commonly ovate-lanceolate and narrowed at the base, dentate or entire. Flowers pink and fragrant. In thickets. 5. Pyrus loensis, Bailey. (Latinized form, meaning pertaining to Iowa.) WESTERN CRAB APPLE. Resembling Pyrus coronaria, but the leaves are white- pubescent on the lower surface, oval or ovate, usually narrowed at the base. Fruit, dull green with small light dots. In thickets. 6. Pyrus Japonica, Thunb. (Latinized form, signifying relating to Japan.) JAPAN QUINCE. A cultivated, thorny, and much-branched shrub from Japan. Flowers scarlet red, produced in great abundance before the leaves. Leaves oval or wedge-oblong. Fruit hard and green ; speckled. XI. AMELANCHIER. Juneberry. Service Berry. Shad Bush. . (Savoy name of the medlar.) Shrubs or small trees, with solitary or racemose white flowers and simple, petioled, serrate leaves. Calyx campanulate and more or less adnate to the ovary, with 5 narrow, reflexed, persistent lobes. Styles 2-5, cavities of the ovary becoming twice as many, with I ovule in each cavity. Pome small and berrylike, 4-io-celled. 64 Introduction to Botany. 1. Amelanchier Canadensis, T. & G. SHAD BUSH or SERVICE BERRY. A tree, seldom more than 25 feet high, with ovate or ovate-lanceolate leaves, acute or acuminate at the apex, and rounded or cordate at the base. Flowers in spreading or drooping racemes, pedicels long and slender. Bracts and stipules long, silky- ciliate. The sweet pome globose, red or purple. In dry woodlands. 2. Amelanchier rotundifdlia, Rcem. (L., rotundus, round; folium, leaf.) ROUND-LEAVED JUNEBERRY. Similar to the above, but with leaves ovate to orbicular, and more or less rounded at both ends. In woods and thickets. 3. Amelanchier alnifdlia, Nutt. (L., alnus, alder; folium, leaf.) NORTH- WESTERN JUNE or SERVICE BERRY. Shrub 3 to 8 feet high. Leaves elliptic to orbicular, serrate above the middle. Flowers in short, dense racemes. A bloom on the purple, globose pome. In dry soil. XH. CRATAEGUS. Hawthorn or White Thorn. (Gr. kratos, strength, referring to the toughness of the wood.) Thorny shrubs or small trees. White or pink flowers in terminal, corymbose clusters. Leaves simple and often lobed. Receptacle (so- called calyx tube) cup-shaped, adherent to the 1-5 carpels. Sepals or calyx lobes 5 ; petals 5 ; stamens numerous. Pome small and drupe- like with 1-5 i -seeded stones. 1. Crataegus Crfls-galli, L. (L., crus, leg; galli, genitive of gallus, a cock.) COKSPUR THORN. Shrub or small tree, with obovate or oblanceolate, serrate leaves, glabrous, shining above and dull beneath. Stems with slender thorns, which are 2 to 4 inches long. Fruit globular and red. In thickets. 2. Crataegus coccinea, L. (L., coccineus, of a scarlet color.) SCARLET THORN or HAW or RED HAW. Shrub or small tree, with stout spines i\ to 2 inches long. Leaves broadly ovate or orbicular, truncate or subcordate at the base, sharply incised and serrate, with glandular-tipped teeth. Glandular pubescence on the calyx and pedicels. Red, globular fruit about \ inch in diameter, sometimes more. In thickets. 3. Crataegus mdllis, Scheele. (L., mollis, soft.) RED-FRUITED THORN or HAW. Similar to Crat&gus coccinea, but with leaves sometimes 5 inches long, usually very pubescent beneath, and hairy fruit, sometimes i inch in diameter. In thickets. 4. Crataegus flava, Ait. (L., flavus, golden yellow.) SUMMER or YELLOW HAW. Small and often quite thorny tree. Leaves obovate, often obtuse and glandular-dentate at the apex, narrowed at the base, at first pubescent on both sides. Fruit globose to pyriform, yellow, red, or greenish. In sandy thickets. 5. Crataegus Oxyacdntha, L. ENGLISH HAWTHORN. Shrubs or trees, with stout and frequent thorns. Leaves generally broadly ovate or obovate, sharply 3~7-lobed, broadly cuneate at the base, i to 2 inches long. Flowers sometimes more than i to 2 inches in diameter, white or pink. Fruit, deep red, globose or ovoid. Roadsides and thickets. Dicotyledones. 65 LEGUMINOS^. PULSE FAMILY. Herbs, trees, or shrubs, with papilionaceous or more or less irregular flowers, and alternate, stipulate, pinnately or palmately compound leaves. Stamens usually 10, monadelphous, diadelphous, or some- times distinct. Ovary superior, of a single carpel, and becoming a legume in fruit. Herbs. Stamens distinct. BAPTISIA I. Stamens diadelphous, or sometimes all united near the base. Leaves palmately 3-foliate. TRIFOLIUM II. Leaves odd-pinnate. ASTRAGALUS VI. Leaves abruptly pinnate. VICIA VII. Herbs or sometimes shrubs. Stamens distinct or united only at the base. Leaves bipinnately compound; stamens 8-12. SCHRANKIA XI. Leaves bipinnately compound; stamens 10-5. DESMANTHUS XII. Stamens monadelphous or diadelphous. PSORALEA III. Trees or shrubs. Stamens distinct or united only at the base. Leaves once or twice pinnately compound. Trees without thorns. GYMNOCLADUS IX. Trees with conspicuous thorns. GLEDITSCHIA X. Leaves simple. CERCIS VIII. Stamens monadelphous; leaves odd-pinnate. AMORPHA IV. Stamens diadelphous; leaves odd-pinnate. ROBINIA V. I. BAPTISIA. False Indigo. (Gr., baptisis, dipping or dyeing.) Erect, perennial herbs, with palmately 3-foliate or rarely simple leaves. Flowers yellow, white, or blue, truly papilionaceous, borne in racemes. Stamens 10 and distinct; ovary stipitate, and pod inflated. Standard about equaling the wings and keel, its sides reflexed. 1. Baptisia tinctoria, R. Br. (L., tinctorius, pertaining to dyeing.) WILD INDIGO. Erect, glabrous, 2 to 4 feet high. Leaves 3-foliate, the leaflets obovate or oblanceolate, petioles short. Flowers yellow. Pods raised on a stipe longer than the calyx, and tipped with the awl-shaped style. In dry soil. 2. Baptisia leucophaea, Nutt. (Or., leukos, white; phaios, gray.) LARGE- BRACTED WILD INDIGO. About i foot high, with divergent branches, pubes- cent throughout. Leaves 3-foliate, sessile, or short-petioled; leaflets spatulate or oblanceolate, with ovate or lanceolate, persistent stipules. Flowers white or cream color, about i inch long, borne in a many-flowered raceme, which sometimes becomes i foot long. Pods hoary, pointed at both ends. On prairies. 66 Introduction to Botany. II. TRIFOLIUM. Clover or Trefoil. (L., tri t three; folium, leaf.) Herbs, with mostly slender branches and 3-foliate leaves, the leaflets denticulate. Flowers pink, purple, white, or yellow, papilionaceous. Stamens 10, diadelphous, or sometimes all united near the base. Flowers in heads or spikes, and pods straight and membranaceous. 1. Trifolium pratense, L. (L., pratensis, growing in a meadow.) RED or MEADOW CLOVER. Flowers red purple, sessile, in globose or ovoid heads, the heads nearly or quite sessile. Somewhat pubescent, branching, perennial herbs. Leaflets short-stalked from the same point, often dark-spotted near the middle. In fields and meadows. 2. Trifolium repens, L. (L., repens, creeping.) WHITE CLOVER. Creeping, mostly glabrous perennials, rooting at the nodes. Leaves rising on long petioles ; leaflets obovate, emarginate-denticulate. Flowers white, in globose heads borne on long peduncles; flowers of the head raised on pedicels. In fields and open places. HI. PSORALEA. (Gr.,psoraleos, scurfy, alluding to glandular dots of the leaves.) Herbs or shrubs, with 1-5 -foliate, glandular-dotted leaves. Flowers bluish purple or white, borne mostly in spikes or racemes. Calyx 5-cleft, the lower lobe longest. Stamens diadelphous, sometimes monadelphous. Ovary i-ovuled; the short pod ovoid and indehiscent. 1. Psoralea tenuiflora, Pursh. (L., tennis, slender, small ; flos, floris, flower.) FEW-FLOWERED PSORALEA. Erect and slender, 2 to 4 feet high, hoary with an appressed pubescence. Leaves short-petioled, digitately 3-5-foliate, mostly oblong- oval or elliptic or obovate, sometimes mucronate at the apex. Peduncles slender and much exceeding the leaves, loosely 6-i4-flowered. Corolla purplish ; corolla about twice the length of the calyx. Prairies. 2. Psoralea argophy^lla, Pursh. (Gr., argos, white; phyllon, leaf.) SILVER- LEAF PSORALEA. Silvery pubescent with white appressed hairs, i to 3 feet tall. Petioles about equaling the leaves. Leaflets 3-5, digitate, oblong-oval to oblong- obovate. Inflorescence interrupted-spicate, peduncles much exceeding the leaves. Flowers deep blue or purplish, about J inch long. Calyx lobes lanceolate, very densely pubescent. Pod ovate, with a straight beak. On prairies. 3. Psoralea floribunda, Nutt. (l^,.,Jlos,floris, flower + adjectival ending, signi- fying plenty.) MANY-FLOWERED PSORALEA. Stems much branched, i to 4 feet high, hoary, not glandular. Leaves mostly 3-5-foliate, sometimes y-foliate. Leaflets oblong, canescent beneath and glandular on both surfaces. Peduncles 2 to 7 inches long, usually many-flowered. Lobes of the calyx triangular-acute. Prairies. 4. Psoralea esculenta, Pursh. (L., esculentus, edible.) POMME BLANCHE. Dicotyledones. 67 PRAIRIE APPLE or TURNIP. 4 to 18 inches high from a tuberous root. Densely hairy all over. Leaves digitately 5-foliate. Leaflets mostly obovate or obovate- oblong. Peduncles often longer than the petioles, bearing dense, oblong, spikelike racemes. Calyx nearly equaling the bluish corolla. Prairies. IV. AMORPHA. False Indigo. (Gr., amorphos, deformed, from the absence of 4 petals.) Shrubs, with odd-pinnate, glandular-punctate leaves. Flowers mostly violet or purple. Corolla consisting of the standard alone, the wings and keel wanting. Stamens 10, monadelphous below, anthers all alike. Pod i-2-seeded. i. Amorpha fruticbsa, L. (L., fruticosus, shrubby.) FALSE INDIGO. A rather tall shrub. Leaflets 11-21, elliptic to oblong. Flowers dense in solitary or clustered spicate racemes. Standard violet-purple. River banks and hillsides. 2. Amorpha microphylla, Pursh. (Gr., mikros, small ; phyllon, leaf.) FRA- GRANT FALSE INDIGO. A bushy shrub, scarcely exceeding i foot in height, nearly glabrous. Standard purplish. Flowers fragrant; racemes mostly solitary. Prairies. V. ROBINIA. Locust Tree. (Named for John Robin, herbalist to Henry IV. of France.) Trees or shrubs, with odd-pinnate leaves and racemes of showy flowers. Stipules often spiny. Calyx 5-toothed, the 2 upper teeth somewhat united. Standard broad and reflexed. Stamens diadel- phous. Ovary several-ovuled. Pods linear and flat, becoming mar- gined on the seed-bearing edge. i. Robinia Pseudacacia, L. (Gv.^pseudcs, false + acacia.) COMMON LOCUST TREE or FALSE ACACIA. Becoming a large tree. Leaflets 9-19; stalked, ovate or oval. Stipules often spiny. Flowers white and fragrant in loose, drooping racemes. Twigs, petioles, and pods glabrous. Extensively planted. vi. ASTRAGALUS. (Ancient Greek name of a leguminous plant.) Chiefly perennial herbs, with odd-pinnate leaves and flowers in racemes. Stamens diadelphous with the anthers all alike. Calyx tubular, the teeth nearly equal. Standard narrow and the keel of the corolla blunt. Pod somewhat turgid, the sutures often projecting so as to divide the cavity into two. i. Astragalus caryocarpus, Ker. (Gr., katyon, a nut ; karpos, fruit.) GROUND PLUM. Flowers violet-purple, about | inch long, in short racemes. Pods globose 68 Introduction to Botany. or oval, sessile, short-pointed, glabrous, fleshy, 2-celled, sometimes i inch in diame- ter. Branches 6 to 15 inches long, ascending or decumbent. Leaflets 15-25, mostly oblong-elliptic. Peduncles equaling or shorter than the leaves. Plant covered with a pale, minute, appressed pubescence. Prairies. 2. Astragalus Mexicanus, A. DC. LARGER GROUND PLUM. Corolla cream color, purplish at the tip, about I inch long. Globose, glabrous pods sometimes exceeding i inch in length, pointless, 2-celled. Pubescence somewhat spreading. Leaflets 17-33, oblong to obovate. Prairies. 3. Astragalus gracilis, Nutt. (L.,gracilis, slender.) SLENDER MILK VETCH. Flowers purple, inch or less in length, in slender, spikelike racemes. Pendent pods i-celled, concave on the back, at first hoary, but becoming glabrous. Plants erect and slender, i to 2 feet high, finely pubescent. Leaflets 11-21, distant and narrowly linear. Prairies. VII. VICIA. Vetch or Tare. (The classical Latin name.) Herbaceous vines, climbing or trailing. Leaves evenly pinnate and tendril-bearing. Stipules mostly half-sagittate. Calyx teeth 5, about equal, or the 2 upper shorter. Standard obovate or oblong, emargi- nate; wings adhering to the middle of the keel. Stamens more or less diadelphous, 9 and i. Style slender, hairy at the summit. 1. Vicia Americana, Muhl. AMERICAN VETCH or PEA VINE. Flowers bluish purple, somewhat less than i inch long, 3-9 in a loose-flowered raceme. Mostly glabrous perennial, 2 to 3 feet long. Leaflets 8-14, elliptic or ovate-oblong, con- spicuously veined. Pod glabrous, 4-y-seeded. In moist soil. 2. Vicia linearis, Green. (L., linearis, linear.) Flowers and fruit as in Vicia Americana, but the leaflets are narrowly linear, and the branches are weak and often zigzag. In dry soil. VIII. CERCIS. Redbud or Judas Tree. (Ancient name of the Oriental Judas tree.) Shrubs or small trees, with red purple flowers in umbellike clusters along last year's twigs or older branches, appearing just before the leaves. Leaves simple, broad, and heart-shaped. Standard in the bud inclosed by the wings. Stamens 10 and distinct. Pods oblong and flat. i. Cercis Canadensis, L. REDBUD. A small tree, often planted for ornamental purposes. In rich soil. Dicotyledones. 69 IX. GYMNOCLADUS. Kentucky Coffee Tree. (Gr., gymnos, naked ; klados, branch, alluding to the somewhat naked branches.) Trees with bipinnate leaves and regular, dioecious, or polygamous, whitish flowers in terminal racemes. Calyx tubular, 5-lobed; petals usually 5, oblong or oval, inserted at the summit of the calyx tube; stamens 10, distinct, shorter than the petals. Pod oblong, 2-valved, thick and leathery, pulpy between the seeds. i. Gymnocladus Canadensis, Lam. KENTUCKY COFFEE TREE. Becoming a large tree with rough bark. The bipinnate leaves quite large, of 7-15 leaflets, the leaflets mostly ovate, acuminate, i to 3 inches long. Racemes many-flowered. Pods 5 to 10 inches long. Rich woods. X. GLEDITSCHIA. Honey Locufet. (Named for J. G. Gleditsch, botanist.) Becoming large, thorny trees. Leaves evenly once or twice pinnate. Flowers small, greenish, in slender, axillary racemes, polygamous. Calyx campanulate, 3-5-cleft; petals 3-5, inserted on the summit of the calyx tube; stamens 6-10, distinct. Pod flat, i -many-seeded. i. Gleditschia triacanthos, L. (Gr., tri, three; akantha, thorn.) THREE- THORNED ACACIA or HONEY LOCUST. Stems often armed with numerous stout, simple, or branching thorns. Leaflets oval to oblong-lanceolate, about i inch long. Pod i foot or more long, shining and twisted, many-seeded ; a sweet pulp between the seeds. Woods and pastures. XI. SCHRANKIA. Sensitive Brier. (Named for F. P. Schrank, botanist.) Perennial herbs or shrubs, prostrate or procumbent, with bipinnate leaves, which are somewhat sensitive, the leaflets small and numerous. Flowers perfect or polygamous, borne in axillary, peduncled heads or spikes. Calyx 5-toothed, minute ; petals united to the middle, 5-cleft above; corolla pink or purple. Stamens 8-12, distinct or united at the base. Plant beset with recurved prickles. Pods spiny, linear, acute, or acuminate. i. Schrankia uncinata, Willd. (L., uncinatus, barbed.) SENSITIVE BRIER. Herbaceous perennial, branches decumbent, 2 to 4 feet long, very prickly. Stems grooved and angled. Pinnae 4-8 pairs. Leaflets obliquely elliptic, 8-15 pairs, prominent elevated veins beneath. Heads very dense, globose. Flowers pink. In dry soil. 7O Introduction to Botany XII. DESMANTHUS. (Gr., desma, a band; anthos, flower.) Perennial herbs or shrubs, with bipinnate leaves and small, regular, greenish, or whitish flowers in peduncled, axillary heads or spikes, per- fect or polygamous. Calyx campanulate, 5-toothed. Petals 5 and dis- tinct or slightly coherent below. Stamens 10 or 5, distinct, exserted. Pod flat, several-seeded. i. Desmanthus brachylobus, Benth. (Gr., brachys, short ; lobos, lobe.) Stems i to 3 feet high, ascending or erect, nearly or quite glabrous. Pinnae 6-15 pairs. Leaflets 20-30 pairs. Stamens 5. Pods curved, oblong, or lanceolate, in globose heads. Prairies and river banks. GERANIACE.. GERANIUM FAMILY. Chiefly herbs, with perfect and mostly symmetrical flowers. Parts of the flower usually in 5's. Stamens commonly as many or twice as many as the sepals, often 5 long and 5 short. Ovary 5-lobed and 5 -celled. Axis of the dry fruit persisting. I. GERANIUM. Cranesbill. (Gr.,geranos, a crane, from fancied resemblance of the long carpels to a beak of the crane.) Herbs with palmately lobed, parted, or divided leaves, and flowers on axillary i -few-flowered peduncles. Stamens 10, 5 long and 5 short. Sepals and petals 5, imbricated in the bud. Ovary 5-lobed and 5-celled, beaked by the compound style; ovules 2 in each cavity. Carpels breaking away from the central axis in dehiscence. 1. Geranium maculatum, L. (L., maculatus, spotted.) WILD or SPOTTED CRANESBILL. Perennials with a thick rootstock. i to 2 feet high, branching above ; pubescent, with more or less spreading hairs. Basal leaves long-petioled, deeply 3~5-parted. Stem leaves shorter, but similar. Petals \ inch long, light purple, bearded on the claw. Sepals hairy and awn-pointed. Carpels pubescent. Woods. 2. Geranium Carolinianum, L. CAROLINA CRANESBILL. Annuals, 6 to 15 inches high, branched from the base, diffuse, loosely pubescent. Leaves 5-9- parted, the divisions cleft into somewhat linear lobes. Flowers whitish or pale rose, in compact clusters; peduncles and pedicels short and hairy. Beak of the hispid-pubescent ovary nearly i inch long. In barren soil and waste places. Dicotyledones. 71 H. OXALIS. Wood Sorrel. (Gr., oxys, sour, relating to the sour juice.) Herbs with sour juice; leaves radical or alternate, mostly of 3 obcor- date leaflets. Sepals 5 and persistent; petals 5, somewhat united at the base. Stamens 10, alternately longer and shorter, mostly mona- delphous at the base. Ovary 5-lobed and 5-celled, the carpels dehis- cing on the back. Styles 5 and distinct. Seeds 2 or more in each cell. Flowers often dimorphous or trimorphous (see Botany, page 176). 1. Oxalis violacea, L. (L., violaceus, violet-colored.) VIOLET WOOD SOR- REL. Perennial, acaulescent herbs from a scaly bulb, 4 to 9 inches high. Scapes umbellately several-flowered, mostly exceeding the leaves. Petals rose-violet, rarely white. Open woods or rocky places. 2. Oxalis stricta, L. (L., strictus, close, tight.) UPRIGHT YELLOW WOOD SORREL. Annual or perennial. Commonly branching at the base, the branches spreading, about 6 inches long. Stems leafy to the top ; flowers yellow. In woods and fields. RUTACE^. RUE FAMILY. Mostly trees or shrubs. Leaves usually compound. Flowers in our species dioecious or polygamous. Sepals and petals 3-5 ; stamens as many or twice as many as the sepals. Pistils 2-5, distinct, or as many carpels united to form a compound ovary. Fruit usually a capsule. Plants secrete a pungent and acrid volatile oil; the foliage dotted with pellucid glands. I. XANTHOXYLUM. Prickly Ash. (Gr., xanthos, yellow; xylon, wood.) Trees or shrubs. Leaves alternate, odd-pinnately compound. The small whitish or greenish flowers dioecious, cymose, axillary, or termi- nal. Sepals and petals 4-5. Stamens 4 or 5. Pistils 2-5, united only by their styles. Stems, and often the petioles, prickly. Pods fleshy, 2-valved, i-2-seeded. i. Xanthoxylum Americanum, Mill. PRICKLY ASH or TOOTHACHE TREE. Shrub with yellowish green flowers appearing before the leaves. Flowers in sessile, axillary, umbellate clusters. Leaves odd-pinnate, leaflets ovate, 5-11. Bark, leaves, and pods very pungent-aromatic. In woods and thickets. Introduction to Botany. EUPHORBIACEJE. SPURGE FAMILY. Herbs, sometimes shrubs or trees, with milky secretions. Flowers monoecious or dioecious. Flowers mostly apetalous, and sometimes much reduced and subtended by an involucre, which resembles a calyx. Stamens few to many, filaments some- times united. Ovary usually 3-celled, with 1-2 ovules in each cavity. Fruit usually a 3-lobed capsule, dehiscing elastically when mature. (Fig. 349.) I. EUPHORBIA. Spurge. (Named for Euphorbus, physician to King Juba.) Flowers without a calyx and clus- tered in a cup-shaped, calyxlike invo- lucre, the cluster easily mistaken by the beginner for a single flower. The flowers of two kinds within the invo- lucre, many staminate flowers consist- ing of a single stamen, and a single pistillate flower consisting of a single 3-lobed pistil protruding above the staminate flowers. Styles 3 and stig- mas 6. Diagrams of the inflorescence of a Euphorbia, i, a single inflores- cence with petal-like involucre and protruding pistillate flower. 2, a staminate flower and accompany- ing bract, which is supposed to rep- resent the calyx. 3, longitudinal diagram of an inflorescence, show- ing the pistillate and four stami- nate flowers. 4, cross diagram of an inflorescence, showing the ovary of the single pistillate flower surrounded by staminate flowers. Around all there is the involucre. i. Euphorbia serpens, H. B. K. (L., ser- pens, creeping.) ROUND-LEAVED SPREAD- ING SPURGE. Annuals, branching from the base, the branches prostrate, slender, 2 to 12 inches long. Leaves orbicular, ovate, or oval, often less than \ inch long, less than twice as long as broad. Stipules triangular and mem- branaceous. In open places. 2. Euphorbia corollata, L. (L., corolla, a little crown.) FLOWERING SPURGE. Perennials from stout rootstocks, I to 3 feet tall, umbellately branched above. Leaves ovate, lanceolate, or linear, only the uppermost opposite or whorled. Involucre with showy white appendages appearing like petals. In dry soil. 3. Euphorbia marginata, Pursh. (L., marginatus, provided with a border.) Dicotyledones. 73 WHITE-MARGINED SPURGE. Erect annuals with stout stems from i to 3 feet high. Bracts of the involucre white-margined and petallike. The uppermost leaves op- posite or whorled and with conspicuous white, petallike margins. In dry soil. ANACARDIACEJE. SUMAC FAMILY. Shrubs or small trees, with acrid, resinous, or milky secretions, mostly alternate leaves, and perfect or polygamo-direcious flowers. Calyx 3-7-cleft, most frequently 5 -cleft, and petals when present of the same number. Stamens usually as many or twice as many as the petals. Ovary i-celled and i-ovuled. Styles 1-3. Fruit generally a small drupe. Sometimes poisonous. I. RHUS. Sumac. (The old Greek and Latin name.) Shrubs or trees, with alternate, odd-pinnate, 3-foliate, or simple leaves. Flowers mostly polygamous in axillary or terminal panicles. Calyx 5-parted, and petals 5. Stamens 5, inserted between the lobes of a flattened disk at the base of the calyx. Fruit generally a small, dry drupe. 1. Rhus. trilobata, Nutt. (Gr., tri, three ; lobos, lobe.) ILL-SCENTED SUMAC or SKUNK BUSH. Shrub 2 to 6 feet high, mostly glabrous. Leaves 3-foliate, the leaflets sessile or nearly so, 5 to i inch long, few lobed or incised toward the summit. Flowers yellow green, in clustered spikes, appearing before the leaves. Unpleasantly scented. Rocky hillsides. 2. Rhus aromatica, Ait. (Gr., aromatikos, pertaining to spice.) (R. Canaden- sts, Marsh.) FRAGRANT or SWEET-SCENTED SUMAC. Similar to the preceding species, but the leaflets 2 to 4 inches long and pleasantly aromatic, and crenate or dentate above the middle. Rocky hillsides. 3. Rhus radicans, L. (L., radicans, having roots.) (R. Toxicodendron in Gray's " Manual.") POISON IVY or POISON OAK. Woody; climbing trees, etc., by means of adventitious rootlets. Sometimes shrubby and not climbing. Leaves 3-foliate, leaflets i to 4 inches long, the terminal longer stalked than the lateral leaflets. Flowers green in loose, axillary panicles. In thickets and low grounds. 4. Rhus hirta, Sudw. (L., hirtus, hairy.) STAG-HORN SUMAC. Large shrub or small tree. Leaves pinnate, with 11-31 leaflets. Leaves and twigs with a velvety pubescence. In dry and rocky soil. 5. Rhus glabra, L. (L.,glaber, bald.) SMOOTH or SCARLET SUMAC. Shrub or small tree. Leaflets 11-31. Foliage and twigs glabrous and somewhat glaucous. In dry soil. 74 Introduction to Botany. SAPINDACEJE. SOAPBERRY FAMILY. Trees or shrubs, with simple or compound leaves. Flowers mostly unsymmetrical and often irregular. Sepals and petals 4-5. Stamens 5-10, inserted in a fleshy disk. Ovary 2-3-lobed, with as many cells. Ovules 1-2 in each cell. I. ACER. Maple. (Latin name of the maple.) Mostly trees, with palmately lobed, opposite leaves and small, polygamo-dioecious flowers. Calyx usually 5 -lobed or parted; petals of the same number or wanting. Stamens 3-12. The 2-celled ovary with a pair of ovules in each cell. Styles 2, stigmatic along their inner surfaces. Fruit, 2 diverging, long- winged samaras, joined together at their bases. 1. Acer dasycarpum, Ehrh. (Gr., dasys, dense or thick; karpos, fruit.) SIL- VER, SOFT, or WHITE MAPLE. Becoming large trees. Leaves (white and some- what pubescent beneath) deeply 5-lobed, 4 to 6 inches long, the lobes irregularly dentate. Flowers greenish or reddish, in dense, sessile, lateral clusters, appearing before the leaves. Petals none. Ovary woolly when young. Along streams, 2. Acer saccharinum, Wang. (Gr., sakckaron, cane or palm sugar.) SUGAR or ROCK MAPLE. Large trees, whose sap yields most of the maple sugar of com- merce. Leaves 3-y-lobed, with rounded sinuses, pale beneath and dark green above. Flowers in lateral or terminal corymbs on long, slender, drooping, hairy pedicels, appearing with the leaves. In rich woods. 3. Acer Negiindo, L. (New Latin for a native name.) Box ELDER or ASH- LEAVED MAPLE. (Negundo aceroides, Mcench, in Gray's " Manual.") Trees with pinnately 3~5-foliate leaves. Flowers dioecious, appearing shortly before the leaves, greenish in drooping clusters. Along streams. H. STAPHYLEA. Bladder Nut. (Gr., staphyle, a cluster.) Upright shrubs, with opposite, 3-foliate, or pinnate leaves and pani- cles or racemes of white flowers terminating branchlets of the current season. Lobes of the 5-parted calyx erect and whitish ; petals 5, inserted on the margin of a thick disk at the base of the calyx. Sta- mens 5, alternating with the petals. Carpels 3, united along their inner faces, and forming in fruit a 3-lobed and 3-celled pod, membranous and inflated. Dicotyledones. 75 i. Staphylea trifolia, L. (L., tri, three ; folium, leaf.) AMERICAN BLADDER NUT. Branching, 6 to 15 feet high. Leaflets mostly 3, ovate-acuminate. Flowers white, campanulate. Carpels in fruit separate at the summit and dehiscing along their inner margins. In moist woods and thickets. m. AESCULUS. Horse-chestnut or Buckeye. (Latin name of an oak tree.) Trees or shrubs. Leaves opposite, palmately 3~9-foliate. Flowers in terminal panicles. Calyx unequally 5-lobed or cleft. Petals 4-5, unequal. Stamens usually 7, filaments slender and often unequal. Ovary 3-celled with 2 ovules in each cell. Style slender. Fruit, a leathery 3-celled and 3-seeded capsule; sometimes 2 seeds become abortive. Seeds large with thick and shining coat ; scar of the seed large and pale. 1. ^sculus glabra, Willd. (L.,glaber, without hair.) FETID or OHIO BUCK- EYE. Trees. Leaflets 5-7, mostly 5 ; 3 to 6 inches long. Flowers pale yellow, in loose, pubescent panicles. Woods and river banks. 2. ./Esculus arguta, Buckl. (L., argutus, fiery.) SHRUBBY or WESTERN BUCKEYE. Shrub, 3 to 10 feet high. Leaflets 7-9, narrow, 3 to 4 inches long. Flowers yellow with reddish center, in dense panicles. Along streams and in moist woods and thickets. RHAMNACE^. BUCKTHORN FAMILY. Shrubs or small trees, sometimes with thorny branches. Leaves simple and alternate. Flowers small and sometimes apetalous, often polygamous, and in some instances dioecious. The limb of the obconic or cylindric calyx tube 4-5 -toothed. Petals 4-5, inserted on the calyx. Stamens of the same number as the petals and inserted with and oppo- site them. Petals more or less concave or hooded in the bud. Ovary 2-5 -celled, with i ovule in each cavity. Stigmas 2-5. Fruit, a drupe or capsule, often 3-celled. I. RHA'MNUS. Buckthorn. (The ancient Greek name.) Shrubs or small trees, with flowers in axillary clusters, greenish, polygamous, and dioecious. Calyx somewhat urn-shaped, lined with a fleshy disk below, its limb 4-5-toothed. Petals 4-5, or none, emargi- nate and hooded, short-clawed. Ovary 3-4-celled and free from the disk. Drupe berrylike, containing 2-4 separate nutlets. j6 Introduction to Botany. 1. Rhamnus lanceolata, Pursh. (L., lanceolatus , armed with a little lance.) LANCE-LEAVED BUCKTHORN. A tall shrub with thornless branches. Leaves ovate-lanceolate, short-petioled, minutely serrulate. Greenish flowers in groups of 2 or 3 in the axils of the leaves. Drupe containing 2 grooved nutlets. In dry soil. 2. Rhamnus alnifolia, L'Her. (L., alnus, alder ; folium, leaf.) ALDER-LEAVED BUCKTHORN or DWARF ALDER. A small shrub with thornless branches. Leaves oval to elliptic, serrated. Flowers greenish, 2 or 3 together in the axils, dioecious, without petals, appearing with the leaves. In swamps. 3. Rhamnus Caroliniana, Walt. CAROLINA BUCKTHORN. Thornless shrub or small tree. Leaves broadly oblong or oblong-elliptic. Flowers several together in axillary, peduncled umbels. Petals present. Drupe globose and sweet, contain- ing 3 seeds. In swamps and along rivers. H. CEANOTHUS. New Jersey Tea or Redwood. (Gr., keanothos, a kind of thistle.) Shrubs, with white, blue, or yellow flowers in axillary or mainly terminal, clustered umbels. Calyx mostly hemispheric and 5-lobed. Petals 5, spreading, incurved, and clawed. Ovary adnate to the disk at the base of the calyx, 3-lobed. Style short and 3-cleft. Fruit 3- lobed, and separating at maturity into 3 nutlets. 1. Ceanothus Americanus, L. NEW JERSEY TEA or REDROOT. Stems ascending or erect, generally several together from a deep reddish root. Leaves ovate to ovate-lanceolate, finely pubescent, particularly beneath. Flowers white. In dry, open woods. 2. Ceanothus ovatus, Desf. (L., ovatus, egg-shaped.) SMALLER REDROOT. Similar to the preceding species, but the leaves are oblong or oval-lanceolate, and nearly glabrous. On prairies and in rocky places. VITACE^I. GRAPE FAMILY. Woody vines trailing or climbing mostly by tendrils. Leaves mostly palmately lobed, dentate, or compound. Flowers small and greenish, polygamous or dioecious. Petals 4-5, hypogynous or perigynous, fall- ing away without expanding. Limb of the calyx mostly obsolete or 4~5-lobed. Stamens of the same number as the petals and opposite them. The single ovary often immersed in a fleshy disk, 2-6-celled, with 1-2 ovules in each cavity. Fruit, a i-6-celled, but commonly 2-celled berry. Stigma slightly 2-lobed, on a short style or sessile. Dicotyledones. 77 I. VITIS. Grape. (The Latin name.) Plants climbing high by coiling tendrils. Leaves simple, rounded, variously sharply-incised, and lobed. Flowers polygamo-dicecious, sometimes perfect, borne in a compound thyrse. Petals falling off without expanding. Five nectariferous glands alternating with the stamens. Fruit, a pulpy, edible berry. 1. Vitis aestivalis, Michx. (L., cestivalis, pertaining to summer.) SUMMER or SMALL GRAPE. Terete branches climbing high. Leaves large, dentate, or 3-5- lobed ; young leaves and branches quite woolly. Tendrils and flower clusters not present opposite each third leaf. Berries sour, but edible, with a bloom. In thickets. 2. Vitis cinerea, Englm. (L., cinereus, ashy.) DOWNY GRAPE. Climbing. Branches angled. Leaves entire or only slightly 3-lobed, dentate; pubescence whitish or grayish, especially pronounced on the under side of leaf. Berries with- out bloom, black, edible, somewhat sour. 3. Vitis riparia, Michx. (L., riparius, relating to a river bank.) RIVERSIDE or SWEET-SCENTED GRAPE. Climbing or trailing. Branches only slightly angled or rounded. Plant glabrous throughout. Leaves shining, mostly sharply 3-7- lobed ; stipules % to \ inch long, persisting until the fruit is formed. Berries bluish black, with a bloom, sweetish, approaching \ inch in diameter. Along rocky stream banks or near water. 4. Vitis cordifblia, Michx. (L., cor, cordis, heart ; folium, leaf.) FROST or CHICKEN GRAPE. Climbing. Branches round or only slightly angled. Leaves shining above, only slightly pubescent beneath, acuminate, very coarsely serrate, sometimes slightly 3-lobed, cordate at the base; stipules small. Berries black and shining, ripening after frost. In moist thickets and along streams. H. AMPELOPSIS. Virginia Creeper. (Gr., ampelos, a vine; opsis, appearance.) Mostly climbing, woody vines. Leaves digitately 3-5, mostly 5- foliate. Leaflets oblong-lanceolate, sparingly serrate above. Tendrils with clinging, suckerlike disks at their tips. i. Ampelopsis quinquefolia. (L., quinque, five; folium, leaf.) VIRGINIA CREEPER, FALSE GRAPE, or AMERICAN IVY. Climbing high on trees or walls. Clinging sometimes by rootlets as well as by tendrils. Flowers in panicles, which are spreading in fruit. Berries bluish. In woods and thickets. Commonly planted for covering walls. 78 Introduction to Botany. TILIACE^. LINDEN FAMILY. Mostly trees or shrubs. Leaves simple and generally alternate, with small, deciduous stipules. Flowers axillary or terminal, cymose or paniculate. Sepals mostly 5, valvate. Petals of the same number as the sepals, sometimes less or wanting, mostly valvate. Stamens many, 5-io-adelphous. Ovary 2-io-celled. Styles lobed or entire. Pedun- cles springing from a leaflike expansion. I. TILIA. Linden or Basswood. (The classical Latin name.) Trees, with serrate, cordate, somewhat inequilateral leaves, and white or cream-colored flowers. Sepals and petals 5. Stamens many, coher- ing in 5 sets (5-adelphous) . Ovary 5-celled with 2 ovules in each cell. Style i ; stigma 5 -toothed. Fruit, 1-2 -seeded, drupaceous. 1. Tilia Americana, L. BASSWOOD or AMERICAN LINDEN. A large tree. Leaves 2 to 5 inches wide, smooth on both sides. Flowers fragrant and much visited by bees for nectar. Along river bottoms. 2. Tilia heterophylla, Vent. WHITE BASSWOOD. Leaves whitened beneath with a downy pubescence. In mountainous, wooded districts. MALVACEJE. MALLOW FAMILY. Herbs or shrubs, with alternate leaves having small, deciduous stipules. Flowers mostly perfect, often showy. Sepals mostly 5 and valvate, somewhat united at the base. Petals of the same number and convolute in the bud. Stamens many, united by their filaments around the pistil, and adherent to the bases of the petals. Anthers i-celled. Ovary of several cells, entire or lobed. Styles united below, but separate above and usually projecting beyond the stamens. I. MALVA Mallow. (The Latin name.) Herbs. Calyx with a 3-leaved involucre at the base. Stamen-column bearing anthers only at the summit. The numerous styles stigmatic along the inner side. Fruit flattened and circular, of several beakless I -seeded carpels. i. Malva rotundif lia, L. (L., rotitndns, round; folium, leaf.) RouND- LEAVED or RUNNING MALLOW. Procumbent annual or biennial. Leaves round- Dicotyledones. 79 reniform, crenate, with 5~9-rounded, shallow lobes. Flowers bluish white, clustered in the axils, to inch broad. Petals about twice the length of the calyx lobes. Waysides and cultivated grounds. II. CALLIRRHOE. (Gr., kalos, beautiful; rheo, flower.) Herbs, with lobed or divided leaves and showy flowers. Bracts of the involucre when present 1-3. Calyx 5-parted; petals truncated at their apices, as many as the lobes of the calyx. Stamen column anther- bearing at the summit. Carpels about 10-20, united in a circle, each i -seeded, beaked at the apex. 1. Callirrhoe alcaeoides, Gray. (Gr., alkea, wild mallow; eidos, form.) LIGHT POPPY MALLOW. Erect perennial, 8 to 20 inches high from a thickened root. Basal leaves triangular and lobed ; stem leaves digitately divided. Bracts of the involucre none. Flowers pink or white, about i inch broad. Carpels pubescent. In dry soil. 2. Callirrhoe digitata, Nutt. (L., digitatus, having fingers.) FRINGED POPPY MALLOW. Similar in habit to the preceding species. Flowers i\ to 2 inches broad ; petals fimbriate along their upper margin ; red purple to white. Carpels hardly pubescent. In dry soil. 3. Callirrhoe involucrata, Gray. (L., involucrum, a wrapper.) PURPLE POPPY MALLOW. Perennials, i to 2 feet long, procumbent or ascending from a deep root. Leaves cordate-orbicular, palmately lobed or incised. Bracts of the involucre 3. Peduncle slender and i-flowered. Flowers red purple, i to 25 inches broad. Carpels rugose-reticulate. In dry soil. VIOLACE^E. VIOLET FAMILY. Herbs, with irregular, i -spurred corolla and adnate anthers conniving over the ovary. Ovary i -celled with 3 parietal placentae. Sepals 5 and petals 5. Leaves stipulate ; flowers nodding. Style club-shaped with a i -sided stigma. I. VIOLA. Violet or Heart's-ease. (The classical Latin name.) Herbs, with basal leaves commonly clustered. Flowers usually scapose and solitary, nodding, often of two kinds, open and showy, and cleistogamous and inconspicuous beneath the leaves. Sepals more or less auricled. Lower petal spurred at the base, and the two lower anthers with spurlike nectaries. Capsule dehiscing into 3 valves. 8o Introduction to Botany. Acaulescent from a rootstock. Flowers various shades of violet and purple to almost white. Lateral petals bearded. (a-) Outer leaves crenate-dentate, inner leaves variously palmately lobed. VIOLA PALMATA I. (6) Leaves pedately parted into linear, obtuse lobes. VIOLA PEDATIFIDA II. (c) Leaves reniform to ovate-wedge-shaped, cordate at the base; margins crenate- dentate; plants glabrous. VIOLA CUCULLATA III. (d) Leaves ovate to orbicular-ovate; peduncles and other parts of the plant villous. VIOLA SOKAKIA IV. Lateral petals beardless. (a) Leaves pedately parted or divided. VIOLA PEDATA V. (6) Leaves ovate to orbicular, cordate at the base, crenate-margined, sweet-scented. Cultivated. VIOLA ODORATA VI. (c) Leaves lanceolate to linear-lanceolate. VIOLA LANCEOLATA VII. Caulescent. Flowers yellow. (a) Leaves reniform to broadly ovate; plant villous or pubescent. VIOLA PUBESCENS VIII. (3) Leaves reniform to ovate, only slightly pubescent; stems slender or decumbent. VIOLA SCABRIUSCULA IX. Flowers various shades of blue or violet to white, rarely yellowish. (a) Leaves ovate to nearly orbicular, acuminate or acute ; stipules ovate to lanceo- late and entire. VIOLA CANADENSIS X. (b) Leaves as above, but stipules dentate, pinnatifid, or fimbriate. VIOLA STRIATA XI. (c) Leaves varying from nearly orbicular to oblong-ovate or oblong-elliptic; stip- ules large and leaflike, pinnatifid or lyrate. VIOLA TRICOLOR XII. (d) Leaves, etc., similar to the above, but the whole plant smaller and more slender. VlOLA TENELLA XIII. 1. Viola palmata, L. (L., palmatus, hand-shaped.) EARLY BLUE VIOLET. Acaulescent, leaves and flowers arising from a rootstock which is scaly and thick. Outer and lower leaves crenate-dentate, inner leaves variously palmately lobed. Flowers blue of different shades, sometimes nearly white. Lateral petals bearded ; styles beardless. Mostly in woods. 2. Viola pedatifida, Don. (L., pes, pedis, the foot; findo, fidi, to divide.) PRAIRIE VIOLET. Acaulescent. Leaves and flowers from a short, scaly root- stock. Leaves pedately parted into linear, obtuse lobes. Flowers bright blue; lateral petals bearded. On prairies. 3. Viola cucullata, Ait. (L., cucullus, a hood.) MEADOW or HOODED VIOLET. Acaulescent from a thick, scaly rootstock. Leaves varying from reniform to ovate- wedge-shaped, cordate at the base, crenate-dentate. Flowers blue, varying to white ; lateral petals bearded. Plants glabrous, or only slightly pubescent when young. Common in various habitats. 4. Viola sororia, Willd. (L., sororius, sisterly.) WOOLLY BLUE VIOLET. Acaulescent from short and thick rootstock. 'Leaves mostly ovate or orbicular- ovate, pointed at the apex and cordate at the base. Leaves crenate-villous when young, but becoming less so with age; ascending. Flowers blue; petals more or less bearded. Peduncles villous. Mostly in shady, dry soil. Dicotyledones. 5. Viola pedata, L. (L^pedatus, furnished with feet.) BIRD'S-FOOT VIOLET. Acaulescent from a thick, short rootstock. Leaves pedately parted or divided. Flowers fragrant, blue to violet, opening widely ; petals beardless. Stigma beard- less and beakless. On hillsides or in sandy or gravelly soil. 6. Viola odorata, L. (L., odoratus, fragrant.) SWEET VIOLET. 'A native of Europe, cultivated in gardens, and running wild in some localities. Spreading by stolons, which take root at the nodes. Leaves and flowers rising from a thick rootstock. Leaves ovate to orbicular, cordate at the base, crenate on the margins. Flowers mostly blue, varying to white ; petals beardless ; fragrant. 7. Viola lanceolata, L. (L., lanceolatus, armed with a little lance.) LANCE- LEAVED VIOLET. Acaulescent; spreading by stolons, with root at the nodes Leaves and flowers from a slender rootstock. Leaves lanceolate to linear- lanceolate, gradually tapering to a petiole, barely crenate. Flowers white, the lower and lateral petals purplish- veined, beardless. Along streams and in moist meadows. 8. Viola pubescens, Ait. (L., pubescens, hairy.) HAIRY YELLOW VIOLET. Caulescent, villous, or pubescent. Basal leaves long-petioled, withering early. Upper leaves short-petioled. Leaves reniform to broadly ovate, finely crenate- dentate. Flowers yellow, purple-veined; spur short. In woods. 9. Viola scabrisiicula, Schwein. (L., diminutive adjective from scaber, rough.) SMOOTHISH YELLOW VIOLET. Resembling the preceding species, but less pubes- cent, and stems slender and sometimes decumbent ; basal leaves usually persisting through the period of blossoming. In woods and thickets. . 10. Viola Canadensis, L. CANADA VIOLET. Caulescent. Stems tufted and leafy throughout. Leaves ovate, sometimes nearly orbicular, glabrous, finely cre- nate, acuminate, or acute. Stipules entire, ovate to lanceolate. Flowers pale violet to white, purple-veined. In woods of hills or mountains. 11. Viola striata, Ait. (L., striatus, furrowed.) PALE or STRIPED VIOLET. Similar in general aspect to the preceding species, but the stipules are dentate, pinnatifid, or fimbriate; petals cream-colored, light blue, or white, much veined. In moist woods or thickets. 12. Viola tricolor, L. (L. t tri, three; color, color.) PANSY or HEART'S-EASE A native of Europe, cultivated in gardens, and sometimes running wild. Rather stout annuals with leafy stems, and large, leaflike, pinnatifid, or lyrate stipules. Flowers large, especially in cultivation, variously yellow, purple, blue, violet, and white. 13. Viola tenella, Muhl. (L., tenellus, somewhat tender.) FIELD PANSY. A native annual resembling the preceding species, but the plants are more slender, stipules smaller, and flowers smaller. In woods and fields. ONAGRACEJE. EVENING PRIMROSE FAMILY. Annuals or perennials, mostly herbaceous. Flowers axillary, spicate, or racemose. Ovary inferior, the so-called calyx tube often prolonged far beyond its summit. Calyx usually 4-lobed, sometimes 2-6-lobed. 82 Introduction to Botany. Petals usually 4, sometimes 2-9, convolute in the bud. Stamens as many or twice as many as the petals, and inserted with them on the tube of the calyx. Ovary usually 4-celled ; stigmas 2-4-lobed or capitate. Pollen often bound together by cobwebby threads. I. (ENOTHERA. Evening Primrose. (Old name for a species of Eptlobium.) Calyx tube prolonged beyond the ovary. Petals and lobes of the calyx 4. Lobes of the calyx reflexed. Stamens 8, the anthers mostly versatile. Ovary elongated and 4-celled. Pollen cobwebby. Flowers white, yellow, or rose-color. 1. (Enothera biennis, L. (L., bi, twice; annus, year.) COMMON EVENING PRIMROSE. Erect and mostly stout annuals or biennials, i to 5 feet high, more or less pubescent. Leaves lanceolate, acute, or acuminate at the apex, narrowed toward the base, sessile or short-petioled, i to 6 inches long, repand-denticulate. Flowers opening in the evening, bright yellow, i to 2 inches broad. Calyx tube i to 25 inches long; reflexed lobes of the calyx cohering at their tips. 2. (Enothera speciosa, Nutt. (L., speciosus, showy.) SHOWY PRIMROSE. Erect or more or less decumbent perennials, from 6 inches to 3 feet high. Leaves lanceolate to linear-lanceolate, sessile or short-petioled, repand-denticulate or sinuate- pinnatifid, 2 to 3 inches long. Flowers usually few, 13 to 3^ inches broad, white to pale pink. Tube of the calyx rather longer than the ovary. Capsule strongly 8-ribbed. Plant pubescent. Prairies. 3. (Enothera Missouriensis, Sims. MISSOURI EVENING PRIMROSE. Decum- bent perennial with short, silken pubescence. Leaves rather thick, oval to linear or oblong-lanceolate, narrowing to a slender petiole, 2 to 6 inches long, remotely denticulate or entire. Flowers axillary, yellow, 3 to 6 inches broad, very striking. Calyx tube 2 to 6 inches, much exceeding the ovary. Capsules very broadly winged. Crests of limestone hills. UMBELLl'FER^. PARSLEY or CARROT FAMILY. Herbs, mostly with hollow, ribbed stems and compound or decom- pound leaves which clasp the stem at the base. Flowers small in simple or compound umbels ; in the latter case the ultimate umbels are called umbellets ; the whorl of bracts usually subtending the general umbel is called the involucre, while that subtending the umbellet is termed the involucel. Ovary entirely inferior, 2-celled and 2-ovuled ; the limb of the calyx surmounting the ovary either wanting or reduced to a mere 5-toothed border. Styles 2 and filiform, their bases frequently thickened, forming a stylopodium. Petals and stamens 5, inserted on a Dicotyledones. 83 disk crowning the ovary. Fruit consisting of 2 seedlike carpels, each of which bears 5 primary ribs, and often 4 intermediate ones. Longi- tudinal oil tubes commonly occur in the tissue of the carpels between the ribs ; these are best seen in cross sections of the carpels. I. HERACLEUM. Cow Parsnip. (Named for Herakles, Greek form of Hercules.) Tall, stout, and often pubescent perennials, with large, ternately compound leaves and broad, compound umbels of white flowers. Involucre of the general umbel deciduous or none ; bracts of the involucels numerous and linear. Calyx teeth obsolete or wanting. Petals obcordate, the outer commonly larger and 2-cleft. Stylopodium or disklike expan- sion at the base of the style common in this family, thick and conic. Fruit broadly oval, obovate, or orbicular, flattened dorsally, and broadly winged on the sides. Ribs filiform with a single oil tube in each interval between the ribs extending only halfway down the fruit, as seen in cross sections. i. Heracleum lanatum, Michx. (L., lanatus, woolly.) Cow PARSNIP. Stems 4 to 8 feet high, stout, ribbed, and woolly. Leaflets broad, irregularly lobed and cut-toothed, pubescent beneath. In moist ground. FIG. 349. Diagrams of Carum Carvi : i, a single flower; 2, lon- gitudinal diagram of a flower ; 3, ripened fruit ; 4, cross-section of a fruit, showing oil ducts in black. AFTER WOSSIDLO. . H. PASTINACA. Parsnip. (The Latin name, from pastus, food.) Mostly biennial, tall, branching, and glabrous herbs. Leaves pin- nately compound. Flowers yellow in compound umbels; involucre and involucels usually wanting. Calyx teeth obsolete. Stylopodium depressed. Fruit flattened dorsally, winged on the margins, and with filiform ribs on the back : a single oil tube in each interval. i. Pastinaca sativa, L. (L., sativus, that is sown or plan ted.) WILD PARSNIP. Stems 2 to 5 feet high from a fleshy, conic root. Lower leaves about i| feet long, petioled, pinnately compound; upper leaves much smaller; leaflets cut-toothed. Roadsides and waste places. 84 Introduction to Botany. in. PEUCEDANUM. Parsley. (The old Greek name.) Perennial herbs, nearly or quite acaulescent, from thickened roots. Leaves mostly bipinnate or finely dissected. Flowers white or yellow in compound umbels. General involucre wanting, but involucels of several bracts. Calyx teeth mostly obsolete. Fruit orbicular, oval, or oblong, flattened dorsally, and winged on the margins. Dorsal and intermediate ribs filiform; 1-4 oil tubes in the intervals. i. Peucedanum foeniculaceum, Nutt. (L., fceniculum, fennel.) FENNEL- LEAVED PARSLEY. Peduncles 4 to 10 inches high, overtopping the leaves, tomentose or nearly smooth. Leaves twice or thrice pinnate, the segments finely dissected, the petioles sheathing at the base. Bractlets of the involucels united below, tomentose. Flowers yellow. Umbels unequally 3~i2-rayed. Fruit broadly oval and glabrous, with thin lateral wings. Prairies. IV. SANICULA. Sanicle or Black Snakeroot. (From low Latin, sanicula, diminutive of sanus, healthy.) Rather tall, glabrous, perennial herbs, with few palmately lobed or parted leaves, the basal leaves long-petioled ; flowers greenish or yellowish in irregular or compound umbels, capitate in the umbellets. Involucre foliaceous ; involucels of few leaves. Fruit globular, not ribbed, and thickly covered with hooked prickles, each with 5 oil tubes. 1. Sanicula Marylandica, L. BLACK SNAKEROOT or SANICLE. Usually unbranched, from i| to 4 feet high. Leaves 3~7-parted, the divisions obovate to oblanceolate, irregularly serrate and dentate. Leaves of the general involucre 3-cleft ; involucel leaves few and small. Umbels 2-4-rayed. Flowers both perfect and staminate, the staminate in separate heads. Petals greenish white, scarcely exceeding the caJyx. Fruit ovoid and beset with stout bristles ; the styles recurved, longer than the bristles. In rich woods. 2. Sanicula Canadensis, L. SHORT-STYLED SNAKEROOT. Staminate flowers never in separate heads, and styles shorter than the prickles on the carpels. Leaves 3~5-divided, petioled, the divisions sharply serrate. In dry woodlands. 3. Sanicula gregaria, Bicknell. (L..,gregarius, belonging to a herd or flock.) CLUSTERED SNAKEROOT. Stems usually clustered, and yellow petals much sur- passing the calyx, i to 3 feet tall. Leaves 5-divided, the divisions lanceolate to obovate-cuneate. In moist woods and thickets. Dicotyledones. 85 V. CKEROPHYLLUM. Chervil. (Gr., chafro, to gladden; phyllon, leaf. From agreeable odor of the leaves.) Annuals, growing mostly in moist soil. Leaves ternately decom- pound with pinnatifid leaflets. Flowers white, few in the umbellets ; umbels few-rayed. Involucre usually none ; involucels of numerous small bracts. Calyx teeth obsolete ; petals reflexed at the apex. Car- pels more or less 5 -angled. Fruit oblong to linear-oblong. Ribs slender and obtuse ; oil tubes solitary in the intervals. i. Chaerophyllum procumbens, Crantz. (L., procumbens, falling forward.) SPREADING CHERVIL. Stems slender, branched, mostly spreading, more or less pubescent, 6 to 18 inches high. Umbels 2-6-rayed. Flowers few in the umbellets. Fruit linear-oblong and glabrous. In moist ground. VI. OSMORRHIZA. Sweet Cicely. (Gr., osme, a scent; rhiza, root.) Perennial herbs from fleshy, clustered, aromatic roots. Leaves ter- nately decompound. Flowers white in few-rayed umbels. Involucre and involucels wanting or of few bracts. Calyx teeth obsolete ; petals incurved at the apex. Fruit oblong-linear, short-beaked, attenuate at the base, usually quite bristly along the equal ribs. Oil tubes obsolete or none. 1. Osmorrhiza brevistylis, DC. (L., brevis, short; stylus, stem or point.) SHORT-STYLED or WOOLLY SWEET CICELY. Erect, rather stout, becoming branched above, i to 3 feet high, villous pubescent. Lower leaves large, long- petioled, sometimes i foot across. Umbellets on long peduncles, 2-6-flowered. Style and stylopodium about ^ inch long. In woods. 2. Osmorrhiza longistylis, DC. (L., longus, long; stylus, stem or point.) LONGER-STYLED or SMOOTHER SWEET CICELY. Similar to the preceding species, but only slightly pubescent or glabrous, and style and stylopodium about ^ inch long. In woods. VH. ERIGENIA. Harbinger of Spring. ' (Gr., erigeneia, born in the spring.) Low, glabrous, nearly acaulescent plants rising from a deep tuber. Leaves ternately decompound, generally only i or 2. Flowers white in small umbels. Calyx teeth obsolete ; petals flat and entire. Fruit nearly orbicular, incurved at top and bottom; carpels nearly kidney- shaped, each 5-ribbed, and 1-3 small oil tubes in each interval. 86 Introduction to Botany. i. Erigenia bulbosa, Nutt. (L., bulbosus, full of bulbs.) HARBINGER OF SPRING. Stem 3 to 9 inches high with a leaf subtending the general umbel. Petioles sheathing at the base. Pedicels very short in flower. Fruit about j^ inch tall, broader than tall. CORNACE^. DOGWOOD FAMILY. Shrubs or trees, usually with entire leaves. Flowers perfect, polyga- mous, or direcious, in cymes or heads. Ovary inferior. Calyx teeth 4-5 or wanting. Petals 4-5, sometimes none, inserted at the base of an epigynous disk. Stamens inserted with the petals, and of the same number or more numerous. Ovary i-2-celled with a single ovule in each cavity. Style i. Fruit a i -2-celled, i-2-seeded drupe. I. CORNUS. Cornel or Dogwood. (L., cornu, horn, from the hardness of the wood.) Shrubs or trees, with mostly opposite or verticillate leaves, and small white, greenish, or purple flowers in cymes or involucrate heads. Calyx 4-toothed ; petals 4 ; stamens 4. Ovary 2-celled with i ovule in each cavity. Stone of the drupe 2-celled and 2-seeded. 1. Cornus florida, L. (L., fioridus, flowery.) FLOWERING DOGWOOD. A shrub or small tree, with mostly ovate or oval, petioled leaves. Flowers greenish yellow, in heads ; bracts of the involucre i\ to 2$ inches long, white or pinkish, emarginate, strongly veined. Fruit ovoid and scarlet, crowned by the persistent calyx. In woods. 2. Cornus circinata, L'Her. (L., circinatus, rounded.) ROUND-LEAVED COR- NEL or DOGWOOD. Shrub, 3 to 10 feet high. Branches greenish and warty. Leaves orbicular or very broadly ovate, woolly beneath. Flowers in flat cymes ; fruit blue. In shady and rocky places. 3. Cornus sericea, L. (L., sericeus, silken.) SILKY CORNEL or KINNIKIN- NIK. A shrub, 3 to 10 feet high, with purplish, pubescent twigs. Leaves narrowly ovate or elliptical, downy beneath. Calyx teeth lanceolate. Cymes flat. Fruit pale blue. Along streams and in damp woods. 4. Cornus asperif61ia, Michx. (L., asper, rough; folium, leaf.) ROUGH- LEAVED CORNEL or DOGWOOD. Shrub, 3 to 15 feet high; branches brownish and rough pubescent. Leaves ovate or elliptic, acuminate, downy beneath and rough pubescent above. Calyx teeth minute ; fruit white. In dry soil or exposed hillsides. ERICACEJE. HEATH FAMILY. Shrubs or perennial herbs. Ovary superior. Calyx and corolla more or less 4~5-parted or cleft. Stamens usually as many or twice as many as the lobes of the corolla. Anthers usually opening by terminal chinks or pores. Style i ; ovary 3-io-celled. Dicotyledones. 87 I. EPIGAEA. Ground Laurel or Trailing Arbutus. (Gr., epi) upon; ge, the earth. From the trailing habit.) Prostrate, more or less hairy, branching shrubs, with evergreen leaves. Flowers clustered at the end of the branches, white or pink, fragrant. Sepals 5, oblong. Corolla salver-formed, mostly 5-lobed. Stamens 10, attached to the base of the corolla and about as long as its tube. Ovary ovoid, hirsute. Style columnar; stigma 5-lobed. i. Epigaea repens, L. (L., repens, trailing.) TRAILING ARBUTUS. MAY- FLOWER. GROUND LAUREL. Leaves oval, oblong-ovate, or nearly orbicular, thick. Branches 6 to 15 inches long. Flowers appearing very early in the spring, exhaling a spicy fragrance. In sandy woods or rocky soil, especially under ever- green trees. n. GAYLUSSACIA. Tangleberry or Huckleberry. (Named for Gay-Lussac, chemist.) Shrubs, with alternate, entire leaves, sometimes serrated. Flowers in lateral, bracted racemes, small and white or pink. Corolla tube urn- shaped or campanulate, with 5-lobed limb. Calyx tube short, the limb with 5 short lobes or teeth. Stamens 10, included. Anthers tapering upward and opening at the summit. Ovary lo-celled. Fruit a berrylike drupe with 10 seedlike nutlets. 1. Gaylussacia frondosa, T. & G. (L., frondosus, leafy.) BLUE TANGLE or TANGLEBERRY. Erect shrubs, 2 to 4 feet high. Leaves obovate-oblong, blunt, under surface pale and glaucous, and resinous. Flowers in loose racemes, greenish pink, round-campanulate. Fruit globose, dark blue, with a bloom, sweet and edible. In moist woods and thickets. 2. Gaylussacia resinosa, T. & G. (L., resinosus, full of resin or gum.) BLACK or HIGH-BUSH HUCKLEBERRY. Shrub, i to 3 feet high. Branches numerous, erect or ascending, and rigid, somewhat pubescent. Leaves mostly oval or oblong-ovate, when young thickly covered with resinous globules, green on both sides. Inflorescence a i-sided raceme. Bracts shorter than the pedicels and deciduous. Fruit black, without bloom, sweet. Rocky woods and thickets, and in swamps. m. VACCINIUM. Blueberry, Bilberry, Whortleberry, or Cranberry. (The old Latin name.) Shrubs, with alternate and often coriaceous leaves. Flowers small, white, pink, or red, urn-shaped or campanulate, in terminal or lateral racemes, or sometimes solitary. Calyx tube globose and adnate to the ovary, the persistent limb 4~5-toothed or lobed. Stamens 8-10, the 88 Introduction to Botany. anthers becoming tubular above, sometimes awned on the back, open- ing by terminal pores. Ovary 4-5-celled, or 8-io-celled by false partitions. Fruit a many-seeded berry. 1. Vaccinium corymbosum, L. (Gr., korymbos, a cluster.) HIGH-BUSH or TALL BLUEBERRY. Shrub, 6 to 15 feet high. Leaves mostly oblong-ovate or elliptical. Flowers tubular, urn-shaped, appearing with the leaves, in short racemes. Calyx 5-lobed; corolla 5-toothed. Stamens 10. Berries blue, with a bloom, pleasantly acid. In swamps and low thickets. 2. Vaccinium Canadense, Richards. CANADA BLUEBERRY. Low-branching shrub, 6 inches to 2 feet high. Leaves narrowly oval to elliptic-lanceolate, pubes- cent at least beneath. Branches downy. Flowers oblong-campanulate, greenish white, appearing with the leaves. Berries mostly blue, with a bloom. Swamps and moist woods. 3. Vaccinium Pennsylvanicum, Lam. DWARF or LOW-BUSH BLUEBERRY. Similar in general aspect to the preceding species, but branches and leaves nearly or quite glabrous, the branches green and warty. Corolla white or pinkish, slightly constricted at the throat. Berries blue, with a bloom, sweet. Dry hills or dry, sandy soil: PRIMULACEJE. PRIMROSE FAMILY. Herbs, with simple leaves, which are mostly opposite or verticillate, but sometimes alternate. Calyx, with rare exceptions, free from the ovary, mostly 5 -parted. Corolla gamopetalous, the limb usually 5-cleft or lobed. Stamens as many as the lobes of the corolla and opposite- them, inserted on the tube of the corolla or at its base. Ovary i-celled, with a free central placenta bearing many ovules. I. PRIMULA. Primrose or Cowslip. (Latin diminutive of primus, first, alluding to early flowering.) Perennial herbs, with leaves clustered at the base, and flowers often borne in umbels at the end of a scape. Corolla salver-shaped, the tube often enlarging above the insertion of the stamens, 5-lobed, the lobes mostly notched or obcordate. The five stamens not exceeding the tube of the corolla. Ovary superior, oblong, ovoid, or globose ; style filiform, and stigma capitate, dehiscing at the apex into 5 valves or 10 teeth. 1. Primula Sinensis, Sabine. (Latinized form, relating to China.) CHINESE PRIMROSE. Cultivated in greenhouses, etc. Flowers showy, white, purple, or pink. Lobes of the corolla sometimes cut-fringed. Plant downy; leaves variously cut or crisped. Calyx inflated. 2. Primula grandiflora, Lam. (L,.,grandis, large; flos^floris, flower.) TRUE PRIMROSE. Cultivated from Europe. .Sulphur- yellow flowers rising on slender pedicels from the axils of basal leaves, no proper scape being developed. Corolla flat. Leaves somewhat hairy on their under sides. Dicotyledones. 89 H. ANDROSACE. Starfoil. (Greek name of a polyp supposed to be a plant.) Low annual or sometimes perennial herbs, with small, tufted basal leaves, and small white or pink flowers borne in scapose, involucrate umbels. Calyx 5-lobed or cleft, persistent. Corolla salver- or funnel- shaped, contracted at the throat, the tube shorter than the calyx. Stamens 5, included. Ovary globular or turbinate. Capsule 5-valved. i. Androsace occidentalis, Pursh. (L., occidentalis, western.) WESTERN STARFOIL. Small, nearly or quite glabrous annual. Scapes i to 3 inches long, mostly clustered, erect or ascending from fibrous roots. The basal leaves and leaves of the involucre oblong-ovate. Corolla white, shorter than the calyx. Pedicels slender. In dry soil. HI. ANAGALLIS. Pimpernel. (The old Greek name, possibly from ana, again; agallo, to delight in.) Diffuse or erect annual or perennial, with mostly opposite or ver- ticillate sessile or short-petioled leaves, and white, blue, red, or pink flowers on axillary peduncles. Calyx and corolla 5-parted ; corolla rotate, longer than the calyx. Stamens 5, inserted at the base of the corolla, more or less pubescent, distinct or united into a ring at the base. Ovary globose with many ovules. Capsule circumscissile. i. Anagallis arvensis, L. (L., arvensis, belonging to the fields.) COMMON PIMPERNEL. Usually much branched annual. Leaves ovate and sessile, shorter than the peduncles. Slender peduncles recurved in fruit. Lobes of the corolla fringed with teeth or glands. Flowers scarlet, sometimes white, opening only in bright weather. In waste places. IV. CENTUNCULUS. Chaffweed. (Derivation uncertain.) Low, glabrous annuals, with small, alternate, and entire leaves and minute, solitary, axillary flowers. Calyx 4-5 -parted; corolla 4-5-cleft, with urn-shaped tube and spreading lobes, shorter than the calyx. Stamens 4-5, filaments short, inserted on the throat of the corolla. Capsule globose, containing many seeds, circumscissile. i. Centunculus minimus, L. (L., minimus, least.) CHAFFWEED or FALSE PIMPERNEL, i to 6 inches high. Leaves spatulate or obovate, short-petioled. Flowers minute, pink, nearly sessile in the axils of the leaves, mostly 4-parted. In moist soil. 90 Introduction to Botany. V. DODECATHEON. American Cowslip. (Gr., dodeka, twelve; theoi, gods. Pliny's name for the primrose, supposed to be under the care of the gods.) Glabrous perennial herbs, with entire or merely repand basal leaves, and flowers in involucrate umbel terminating a scape. Calyx 5-parted with lobes at first reflexed. Corolla 5-parted with reflexed lobes, the tube short and thickened at the throat. Stamens 5, monadelphous, connivent into a cone, inserted on the throat of the corolla. Ovary ovoid or nearly globose, containing numerous ovules. i. Dodecatheon Meadia, L. AMERICAN COWSLIP or SHOOTING STAR. Peren- nial, with short rootstock and fibrous roots. Leaves mostly oblanceolate, narrow- ing into a petiole, entire or sometimes toothed. Scape 8 inches to 2 feet high. Corolla pink, purple, or white. Often cultivated. Rich woods and prairies. EBENACE^. EBONY FAMILY. Trees or shrubs, with alternate, exstipulate, entire leaves and polyga- mous, regular flowers. Calyx 3~7-lobed, free from the 3-i2-celled ovary. Corolla gamopetalous, 3-7-lobed. Stamens inserted on the tube of the corolla, and 2 to 4 times as many as its lobes. Fruit a berry containing I or more seeds, with bony testa. I. DIOSPYROS. Date Plum or Persimmon. (Gr., dies, of Jove; pyros, grain.) Trees or shrubs, with simple leaves and lateral, solitary, or clustered, direciously polygamous flowers. Corolla urn-shaped, 4-6-lobed. Calyx 4-6-lobed. Stamens 8-20 in the sterile flowers, fewer and imperfect, or even wanting, in the pistillate flowers. Ovary globose or ovoid ; styles 2-6. Berry large and pulpy, containing 4-12 hard and flat seeds. i. Diospyros Virginiana, L. COMMON PERSIMMON. Tree, with hard and dark bark. Leaves thickish, ovate-oblong to oval, nearly or quite glabrous. Calyx 4-parted. Corolla mostly 4-lobed, greenish yellow, thickish, campanulate, or some- what urn-shaped ; sterile flowers smaller than the fertile. Fruit very astringent when green, becoming reddish yellow, and sweetening after exposure to frost. Woods and old fields. OLE ACE JE. OLIVE FAMILY. Trees or shrubs, with mostly opposite, pinnate, or simple exstipulate leaves, and flowers in panicles, cymes, or fascicles. Calyx 4-cleft or obsolete ; corolla 4-cleft, or 4-petalous, or sometimes wanting. Stamens Dicotyledones. 91 2-4, mostly 2, inserted on the corolla. Ovary superior, 2-celled, and with 2, or at most a few, ovules in each cavity. Fruit a berry, drupe, samara, or capsule. I. SYRINGA. Lilac. (Gr., syrinx, a pipe, possibly relating to the narrow tube of the corolla.) Shrubs, with simple, entire, opposite leaves and dense panicles of gamopetalous flowers. Calyx mostly 4-toothed. Corolla salver-formed with a 4-lobed limb. Stamens 2, inserted near the summit of the corolla tube. Ovary 2-celled with 2 ovules in each cell. Style elongate ; stigma 2-cleft. Fruit a narrowly oblong capsule. Natives of the Old World, cultivated for ornament. 1. Syringa vulgaris, L. (L,., vulgaris, common.) COMMON LILAC. A shrub, common in gardens. Leaves ovate, somewhat cordate at base, acuminate at the apex, green and smooth on both sides. Flowers lilac or pale violet, in compact, terminal panicles or thyrses appearing soon after the leaves, fragrant. A white variety also occurs. 2. Syringa Persica, L. PERSIAN LILAC. Base of leaves narrower and some- what tapering ; leaves nearly lance-ovate. H. FRAXINUS. Ash. (The classical Latin name.) Trees, with opposite, odd-pinnate leaves and polygamous or dioecious flowers in dense panicles or racemes in the axils of last year's leaves. Calyx small, 4-cleft, or toothed, or entire, sometimes wanting. Petals 2-4, or wanting. Stamens usually 2, sometimes 3-4. Fruit a flat samara, winged all around or only at the apex. 1. Fraxinus Americana, L. WHITE ASH. A tall tree. Leaflets 5-9, mostly 7, petioled, commonly ovate to ovate-lanceolate, entire or denticulate, dark green above and paler or sometimes pubescent beneath. Flowers dioecious, rarely monoecious. Fruit nearly cylindrical, about half as long as the wing, which springs from its summit. In rich woods. 2. Fraxinus quadrangulata, Michx. (L., quadrus, square ; angulatus, angled.) BLUE ASH. A large tree, with angular twigs and 7-11 chiefly lanceolate leaflets, which are short-stalked, green on both sides, and denticulate or finely serrate. Flowers dioecious. Fruit narrowly oblong, winged on the sides as well as apex ; wing often notched. In woods. ASCLEPIADACE^aL. MILKWEED FAMILY. Perennial herbs or shrubs, usually exuding latex or milk when wounded. Flowers perfect and mostly in umbels. Ovary of 2 carpels, which are united only at the summit with a fleshy, stigmatic disk. 92 Introduction to Botany. Numerous ovules on a parietal placenta in each carpel. Anthers more or less coherent and forming a closed tube around the carpels. Pollen coherent in rather horny masses, called pollinia, the adjacent pollinia of contiguous anthers being joined together by an inverted V-shaped, horny excretion from the stigmatic disk (see Fig. 108). Nectar receptacles occurring as a 5-lobed or parted crown or corona. I. ASCLEPIAS. Milkweed or Silkweed. (Gr., asklepios, god of medicine.) Herbs, usually with opposite or verticillate leaves. Each nectar receptaele bearing an incurved horn within. Calyx usually small, divided into 5 segments ; the 5 corolla segments reflexed when open. Anthers tipped with a scale and winged along the sides. Seeds hairy-tufted in all but i species (see Fig. 129). 1. Asclepias tuberosa, L. (L., tuberosus, full of humps or lumps.) BUTTER- FLY WEED or PLEURISY ROOT. Stems erect or ascending, hirsute-pubescent, milky secretions not exuding when the stems are broken. Leaves alternate, lanceolate-oblong. Flowers orange-colored in terminal cymose umbels. In dry fields. 2. Asclepias deciimbens, L. (L., decumbens, falling down.) DECUMBENT BUTTERFLY WEED. Somewhat similar to the preceding species. Leaves elliptic to oblong. Stems at first decumbent, but erect nearer the apex. In dry fields. 3. Asclepias Cornuti, Decaisne. (L., cornutus, horned.) COMMON MILK- WEED or SILKWEED. Stems erect and stout, 3 to 5 feet high, finely pubescent. Leaves oval-oblong, pubescent beneath. Flowers greenish white with purplish tinge, in dense umbels. Nectar receptacles exceeding the anthers, and incurved horns. Follicles 3 to 5 inches long, tomentose and beset with soft spinose processes. In rich -ground. II. ASCLEPIODORA. (Gr., asklepios, god of medicine; doron, gift.) Similar to Asclepias. but without horns from the nectar receptacles, and with corolla lobes ascending or spreading. i. Asclepiodora viridis, Gray. (L., viridis, green.) GREEN MILKWEED. Stems about i foot high, nearly or quite glabrous. Leaves ovate-oblong to lanceo- late, short petioled, alternate. Flowers green with a purplish crown. In dry soil. CONVOLVULACE^. MORNING GLORY FAMILY. Mostly twining or trailing herbs, sometimes with milky secretions. Leaves alternate. Flowers axillary, solitary, or cymose, regular and perfect. Calyx 5-parted or divided. Corolla gamopetalous, generally Dicotyledones. 93 with an elongated tube, the limb 5 -angled, lobed, or entire. Stamens 5, alternate with the lobes of the corolla, inserted low down in the tube. Ovary superior, 2-3-celled, with 2 erect ovules in each cavity ; or some- times false partitions seem to double the number of cavities, with apparently I ovule in each cell. Fruit, a globular 2-4-valved capsule. I. IPOMOEA. Morning Glory. (Ips, a worm; homoios, like.) Mostly twining or trailing annuals or perennials, with showy, axillary, solitary, or cymose flowers. Sepals 5, sometimes unequal. Corolla salver-shaped to funnel-form, or sometimes nearly campanulate, ^-angled or lobed. Style simple, terminated by i-3-capitate or globose stigmas. Stamens and style often included. Capsule globular, 4-6-seeded and 2-4-valved. 1. Ipomoea pandurata, Meyer. (L., pandura, a sort of fiddle.) WILD POTATO VINE or MAN-OF-THE-EARTH. Nearly smooth perennial, trailing, barely climbing, from a massive root. Leaves broadly cordate, or sometimes angular, 3-lobed or fiddle-shaped. Peduncles i-5-flowered, elongating in fruit. Sepals oblong, obtuse, or acute. Corolla funnel-form, 2 to 3 inches long, white with purple stripes in the throat; limb 5-lobed. In dry soil. 2. Ipomoea leptophylla, Torr. (Gr., leptos, thin ; phyllon, leaf.) BUSH MORN- ING GLORY. Smooth perennial, with erect, ascending, or reclining stem, 2 to 4 feet long from an enormous root. Much branched. Leaves 2 to 5 inches long, linear, acute at the apex, on short petioles. Peduncles i-4-flowered, nearly erect, shorter than the leaves. Sepals broadly ovate. Corolla about 3 inches long, funnel- form, scarcely-lobed, pink or purple. Capsule ovoid, 2-celled, nearly i inch long. In dry soil of western plains. H. CONVOLVULUS. Bindweed. (L., convolvere, to twine.) Mostly perennials, with twining, trailing, or erect stems from slender rootstocks. Leaves mostly cordate or sagittate. Calyx sometimes with a pair of bracts at its base. Corolla funnel-form to campanulate, soli- tary or clustered in the axils of the leaves, white, purple, or pink. Sta- mens included in the tube of the corolla. Style slender ; stigmas "2, linear, awl-shaped, or ovoid. Ovary i -2-celled and 4-ovuled. i. Convolvulus sepium, L. (Gr., sepion, bone of cuttle-fish.) HEDGE or GREAT BINDWEED. Stems 3 to 10 feet long, trailing or twining. Leaves triangular- hastate on slender petioles. Flowers funnel-form on slender peduncles, white or tinged with pink. Two large bracts at the base of the calyx. Stigmas oblong. In fields and waste places, preferring moist soil. 94 Introduction to Botany. 2. Convolvulus repens, L. (L., repens, trailing.) TRAILING BINDWEED. I to 3 feet long, trailing or twining, pubescent or tomentose. Leaves sagittate with basal lobes obtuse or rounded, sometimes cordate. Peduncles i -flowered. Flowers white. Stigmas oblong. Calyx 2-bracted. In dry fields. 3. Convolvulus spithamaeus, L. UPRIGHT BINDWEED. Erect or ascending, 6 to 12 inches high, somewhat pubescent. Leaves mostly oblong-oval and short- petioled. Flowers white, solitary on long peduncles. Calyx subtended by 2 large oval bracts. Stigmas thick, oblong. In dry, sandy, or rocky soil. 4. Convolvulus arvensis, L. (L., arvensis, belonging to the fields.) SMALL BINDWEED. Stems slender, trailing or decumbent, i to 2^ feet long, nearly or quite glabrous. Leaves sagittate at the base and somewhat acute at the apex. Peduncles i-4-flowered, but commonly 2-flowered. Corolla short-funnel-form, white or pink. Peduncles, and usually the pedicels, bracted. Calyx not bracted. Stigmas linear. In fields and waste places. POLEMONIACE^. PHLOX FAMILY. Herbs. Flowers in corymbose or paniculate clusters, perfect and mostly regular. Calyx 5 -cleft, tubular or campanulate. Corolla 5-lobed, tubular, campanulate, or rotate. Stamens 5, inserted on the tube of the corolla and alternate with its lobes. Ovary superior, 3-celled ; style 3-lobed. Capsule few- to many-seeded, 3-valved. I. PHLOX. (Gr., phlox, flame, an ancient name for Lychnis.) Perennial or annual herbs, with opposite, entire leaves, and flowers borne in cymose, mostly bracted, clusters. Calyx tubular or tubular- campanulate, becoming distended and rupturing by the ripening capsule. Corolla salver-form with broad, spreading lobes. Stamens included, inserted at different heights on the corolla tube. Ovules 1-4 in each of the 3 cavities x>f the ovary. 1. Phlox maculata, L. (L., maculatus, stained or spotted.) WILD SWEET WILLIAM. Stems erect, i to 5 feet high. Sometimes puberulent, and often flecked with purple. Leaves, excepting the uppermost, opposite, ovate to ovate- lanceolate, 2 to 5 inches long. Flowers short-pediceled, borne in elongated, leafy panicles. Calyx teeth lanceolate. Flowers mostly pink or purple. 2. Phlox glaberrima, L. (L.,glaberrimus,very smooth.) SMOOTH PHLOX. Stems i to 3 feet high, smooth and slender. Leaves linear-lanceolate, or linear below, 15 to 4 inches long. Flowers in cymes grouped in a corymbose cluster. Calyx teeth lanceolate-awl-shaped. Corolla mostly pink, with obovate lobes longer than the tube. Prairies and open woods. 3. Phlox pildsa, L. (L., pilosus, downy.) DOWNY PHLOX. Stems slender, i to 2 feet high. Plant downy or hairy, sometimes glandular. Leaves i to 4 inches Dicotyledones. 95 long, lanceolate or linear. Flowers in corymbose-cymes. Calyx teeth awl-shaped. Corolla pink, purple, or white with obovate lobes and somewhat pubescent tubes. In dry soil. 4. Phlox divaricata, L. (L., divaricatus, spread out or apart.) WILD BLUE PHLOX. Stems decumbent at the base, spreading, viscid-pubescent, 9 to 18 inches high. Leaves lanceolate to ovate-lanceolate, about i inches long, Flowers in loosely-flowered cymules, blue or lilac, slightly fragrant. Calyx teeth awl-shaped. Lobes of the corolla obcordate, emarginate, or entire, slightly longer than the tube. In damp woods. 5. Phlox subulata, L. (L.,su&ula, an awl.) GROUND or Moss PINK. Stems diffuse, matted, branches 2 to 6 inches long. Leaves mostly linear-awl-shaped or linear-lanceolate, from J to nearly i inch long, ciliate, often fascicled at the nodes and widely spreading. Calyx teeth somewhat awl-shaped. Corolla pink, purple, or white, its lobes shorter than the tube. On rocky or sandy hills or banks. HYDROPHYLLACEJE. WATERLEAF FAMILY. Herbs, with leaves mostly alternate. Corolla gamopetalous, 5-lobed or parted, salver-form to campanulate or rotate. Calyx 5-cleft or divided. Stamens 5, inserted on the tube of the corolla or at its base, alternate with its lobes. Ovary superior, i -celled with 2 parietal pla- centas, or 2-celled by the ingrowth and coalescence of the placentae. Styles 2, sometimes partly united. Fruit, a 2-valved, 4-many-seeded capsule. Flowers in cymes, racemes, or spikes, sometimes solitary. I. HYDROPHYLLUM. Waterleaf. (Gr., hydor, water; phyllon, leaf, application not evident.) Perennial or biennial herbs. Leaves lobed or pinnately divided or parted. Flowers white, blue, or purple, in cymes. Calyx deeply 5 -parted, the divisions lanceolate or awl-shaped. Corolla campanulate, 5-cleft, with a linear, grooved appendage extending down the tube opposite each lobe. Stamens 5, exserted. Filaments bearded. Ovary i -celled, the fleshy placentae nearly filling the cavity, each bearing 2 ovules. Capsule i-4-seeded. 1. Hydrophyllum Virginicum, L. VIRGINIA WATERLEAF. Perennial from scaly rootstock. Nearly or quite glabrous. Stem slender, ascending or erect, i to 3 feet long. Leaves with 5-7 ovate-lanceolate or oblong, pointed, pinnate divisions, the divisions cut-toothed. Peduncles longer than the petioles of the upper leaves. Calyx lobes narrowly linear, ciliate, the sinuses not appendaged. Flowers about i inch long, purplish or white. In woods. 2. Hydrophyllum Canadense, L. BROAD-LEAVED WATERLEAF. Perennial from a scaly rootstock. Stems slender, nearly or quite glabrous, i to 2 feet high. 96 Introduction to Botany. Leaves rounded, cordate at the base, palmately 5-y-lobed, the lobes pointed and unequally toothed, somewhat pubescent. Lower leaves long-petioled and very broad, sometimes nearly i foot in diameter; upper leaves smaller and shorter- petioled. Flowers in cymes, purplish or white. Calyx lobes linear-awl-shaped, smoothish, sometimes with minute appendages in the sinuses. Corolla short- campanulate. In woods. 3. Hydrophyllum appendiculatum, Michx. (L., appendicula, a small appen- dage.) APPENDAGED WATERLEAF. Rough and hairy biennial. Stems slender, i to 2 feet long. Lower leaves long-petioled and pinnately incised or divided, the lobes dentate or incised. Upper leaves smaller, rounded, palmately 5-lobed, the lobes pointed and irregularly toothed. Calyx with a reflexed appendage in each sinus. In damp woods. II. ELLI'SIA. (Named for John Ellis, naturalist.) Slender branching annuals, with pinnately lobed or divided leaves and small white or bluish flowers, solitary or racemed. Calyx spread- ing, 5-lobed or parted, enlarging in fruit. Corolla campanulate or cylindric, hardly, or not at all, exceeding the calyx ; 5 minute appen- dages within the tube. Stamens included. Ovary i -celled; placentae as in Hydrophyllum, each 2-4-ovuled. i. Ellisia Nyctelea, L. (Gr., nyktelios, nightly.) Somewhat hairy, 6 to 12 inches high. Leaves ovate-oblong in outline, the lobes mostly oblong and cut- toothed. Corolla whitish. Peduncles opposite the leaves, i-flowered. In shady and damp situations. BORAGINACE^. BORAGE FAMILY. Mostly rough, hairy herbs, but sometimes shrubs and trees, with alternate, entire leaves and perfect flowers borne in cymes, racemes, or spikes, which are often scorpioid. Calyx 5-lobed, cleft, or parted. Corolla gamopetalous, mostly 5-lobed. Stamens 5, inserted on the tube of the corolla and alternate with its lobes. Ovary superior, mostly deeply 4-lobed. Style undivided or 2-cleft. Fruit appearing like 4 i -seeded nutlets. I. CYNOGLOSSUM. Hound's Tongue. (Gr., kyon, dog; glossa, tongue.) Coarse herbs, with long-petioled basal leaves and mostly sessile upper leaves. Flowers in panicled, somewhat scorpioid racemes. Calyx 5-parted. Corolla funnel-form, its tube about equaling the calyx, and the throat closed by obtuse scales opposite the lobes. Stamens included. Nutlets beset with short, barbed prickles. Dicotyledones. 97 i. Cynoglossum officinale, L. (L., officina, a workshop.) COMMON HOUND'S TONGUE. 15 to 3 feet high. Soft, hairy biennial. Upper leaves lanceolate and sessile ; lower leaves broadly lanceolate, tapering into a long petiole. Flowers in simple or branched racemes, which elongate in fruit. Calyx lobes ovate-lanceolate. Corolla reddish purple, sometimes white, about inch in diameter. Nutlets flattened on their upper face. In pastures and waste places. II. LITHOSPERMUM. Gromwell or Puccoon. (Gr., lithos, stone; sperma, seed, from the hardness of the seeds.) Hairy or rough annual, biennial, or perennial, with alternate, entire, sessile leaves. Roots thick and often reddish. Flowers in leafy-bracted racemes or spikes, or solitary. Calyx 5-cleft or parted, with narrow lobes. Corolla salver-form or funnel-form, sometimes crested or pubes- cent in the throat. Stamens 5, included, inserted on the tube of the corolla and alternate with its lobes. Nutlets 4 or less, white and shining or brown and wrinkled. 1. Lithospermum canescens, Lehm. (L., canescens, becoming hoary.) HOARY PUCCOON. Perennial, pubescent, and somewhat hoary, 6 to 18 inches high. Leaves oblong or ovate-oblong, blunt, downy beneath and roughish above. Flowers in short, leafy racemes. Segments of the calyx linear-lanceolate, shorter than the tube of the corolla. Corolla orange-yellow with rounded, entire lobes, crested in the throat. Nutlets white, smooth, and shining. On prairies or in open woods. 2. Lithospermum angustifolium, Michx. (L., angustus, narrow ; folium, leaf.) NARROW-LEAVED PUCCOON. Pubescent and rough perennial from a deep root, 6 to 18 inches high. Leaves linear and acute. Flowers in terminal, leafy racemes. The early flowers more showy and with longer tubes than the later. Corolla of the early flowers about i inch long, bright yellow, the tube much longer than the seg- ments of the calyx, the lobes erose-denticulate, and the throat crested. Pedicels of the later, cleistogamous flowers recurved in fruit. Nutlets white and shining, often punctate. On prairies or in dry soil. 3. Lithospermum arvense, L. (L., arvum, a plowed field.) CORN GROM- WELL. Rough, somewhat hoary. Leaves lanceolate to linear. Flowers whitish ; corolla scarcely longer than the calyx ; throat naked. In waste soil. III. ONOSMODIUM. False Gromwell. (Named from resemblance to genus Onosma.) Stout-bristly or rough-pubescent perennial herb, with alternate, entire, prominently veined leaves and white, greenish, or yellowish flowers in leafy-bracted scorpioid racemes or spikes. Calyx with 5 narrow seg- ments. Corolla tubular or tubular-funnel-form with 5 erect lobes. 98 Introduction to Botany. Stamens 5, included, inserted on the tube of the corolla. Style filiform, long-exserted. Ovary 4-parted, but producing only 1-2 white, shining nutlets. 1. Onosmodium Carolinianum, DC. SHAGGY FALSE CROMWELL, i to 3 feet high, beset with rough, spreading hairs. Leaves lanceolate or ovate-lanceo- late, acute. Corolla pubescent outside, yellowish white. On prairies or in dry fields. 2. Onosmodium mdlle, Michx. (L., mollis, soft.) SOFT-HAIRY FALSE GROM- WELL. i to 2 feet high, pale, clothed with short, soft hairs. Leaves ovate-lanceo- late, acute. On prairies. 3. Onosmodium Virginianum, DC. VIRGINIA FALSE GROMWELL. i to 2 feet high. Clothed with short, appressed, bristly hairs. Leaves oblong to oblong- lanceolate, blunt, oblanceolate below, narrowing to a petiole. Corolla yellowish white. On hillsides or banks or in dry thickets. VERBENACE^E. VERVAIN FAMILY. Herbs or shrubs, with mostly opposite or verticillate leaves. Flowers somewhat 2-lipped, or regular, in spikes, racemes, cymes, or panicles. Calyx 4-5-lobed or cleft. Corolla mostly with cylindric tube and 2- lipped or 4~5-lobed and regular. Stamens 4, didynamous, or as many as the lobes of the corolla, sometimes only 2, inserted on the tube of the corolla. Ovary superior, mostly 2-4-celled, but not 4-lobed. Style simple ; stigmas 1-2. Fruit separating at maturity into 2-4 nutlets. I. VERBENA. (Latin name for any sacred herb.) Herbs, with opposite leaves and flowers in terminal, simple, or pani- cled spikes. Calyx tubular, 5 -angled, or toothed. Corolla salver-form or funnel-form, with spreading, 5-lobed limb. Stamens 4, didynamous, or rarely 2, included. Ovary 4-celled with i ovule in each cavity. Fruit splitting into 4 nutlets. 1. Verbena Aubletia, L. LARGE-FLOWERED VERBENA. Perennial, i foot high or less, soft pubescent or smoothish. Leaves ovate to ovate-oblong in out- line, incisely lobed or toothed, or 3-cleft, the lobes dentate. Inflorescence capitate, but becoming spicate. Bracts of the inflorescence shorter than, or hardly equaling, the calyx. Calyx teeth slender, awl-shaped. Corolla reddish purple or lilac, rarely white, about i inch long, and the limb inch or more in diameter. On prairies or in open woods. 2. Verbena bipinnatffida, Nutt. (L., bi, twice; pinnatus, feathered; findere, to cut.) SMALL-FLOWERED VERBENA. Perennials, producing suckers, erect, 6 to Dicotyledones. 99 18 inches high. Leaves i-2-pinnatifid into oblong or linear divisions. Spikes solitary at the ends of the branches. Bracts of the inflorescence mostly exceeding the calyx. Corolla bluish purple or lilac, limb of the corolla less than 5 inch broad. On open prairies. 3. Verbena bractedsa, Michx. (L., bractea, a thin plate.) LARGE-BRACTED VERVAIN. Perennial. Stems 4-sided ; much branched from the base, the branches decumbent or ascending, 6 to 15 inches long. Leaves wedge-lanceolate in outline, short-petioled, cut-pin natifid, or 3-cleft. Spikes dense, becoming 4 to 6 inches long, with conspicuous bracts longer than the purple flowers. Corolla about | inch long. On prairies and in waste places. LABlATJE. MINT FAMILY. Aromatic herbs or shrubs, with opposite leaves and usually 4-sided stems. Flowers chiefly in cymose clusters, which are often aggregated into spikes or racemes. Calyx mostly 5-toothed or lobed, persistent. Corolla gamopetalous, mostly 2-lipped, the limb 4~5-lobed. Stamens mostly 4 and didynamous, inserted on the tube of the corolla, some- times only 2. Ovary superior and deeply 4-lobed, with I ovule in each lobe. Fruit, 4 seedlike nutlets at the bottom of the persistent calyx. I. SCUTELLARIA. Skullcap. (L., scutella, a dish, alluding to calyx in fruit.) Bitter annual or perennial herbs. Flowers in spikelike racemes, blue or violet. Calyx 2-lipped, the upper lip with a prominent protuberance. Corolla 2-lipped, its tube long, ascending, and somewhat curved, dilated in the throat; the upper lip arched and the lower spreading or bent downward. Stamens 4, all anther-bearing, didynamous, the lower anthers but i -celled. Ovary 4-parted ; style unequally 2-cleft. Lips of the* calyx closed in fruit. 1. Scutellaria serrata, Andrews. (L., serratus, notched like a saw.) SHOWY SKULLCAP. Slender perennial, i to 2 feet high, nearly glabrous. Leaves ovate to ovate-oblong, coarsely serrate or dentate. Flowers in terminal loose racemes. Corolla blue, about i inch long, very minutely pubescent, the upper lip somewhat shorter than the lower. In woods. 2. Scutellaria pilosa, Michx. (L.,pilosus, hairy.) HAIRY SKULLCAP. Peren- nial, clothed with spreading hairs. Leaves ovate to oval or oblong, crenate or coarsely serrate, i to 3 inches long, rather remote, the lower long-petioled. Racemes short. Corolla blue, about inch long, the lower lip a little shorter than the upper. In dry woods or thickets. 3. Scutellaria Wrightii, Gray. (Latin genitive of proper name.) RESINOUS SKULLCAP. Perennial from a woody root, 6 to 10 inches high. Minutely hairy ioo Introduction to Botany. and generally resiniferous. Leaves ovate to spatulate-oblong, entire, obtuse, from 4 to 5 inch long. Flowers solitary in the axils of the upper leaves. Corolla 5 to | inch long, violet to nearly white, pubescent. On western plains. 4. Scutellaria parvula, Michx. (L., parvulus, very small.) SMALL SKULL- CAP. Perennial from slender, tuberiferous rootstocks. Erect or ascending, 3 to 12 inches high. Minutely downy. Lower leaves round-ovate, upper lance-ovate. Flowers solitary in the axils of the upper leaves. Corolla | to 5 inch long, violet, pubescent. In moist, sandy soil. 5. Scutellaria campestris, Britton. (L., campestris, belonging to the field.) PRAIRIE SKULLCAP. Perennial from tuberous-thickened rootstocks. More or less spreading. Leaves ovate, rounded or truncate at the base, often dentate. Minutely pubescent. Flowers violet or purple. Listed by Gray as var. mollis of the preceding species. In dry, sandy soil. 6. Scutellaria nerv6sa, Pursh. (L., nervosus, full of nerves.) VEINED SKULL- CAP. Perennial from slender stolons. Slender, 8 inches to 2 feet high. Lower leaves rounded to ovate, coarsely serrate or dentate, upper leaves ovate-lanceolate and entire. Flowers solitary in the axils of the upper leaves. Leaves prominently nerved beneath. Corolla bluish, about J inch long. Lower lip longer than the concave upper one. In moist thickets or woods. II. NEPETA. Cat Mint. (The Latin name.) Erect or creeping herbs. Flowers in verticillate clusters. Calyx tubular, obliquely 5-toothed. Corolla 2-lipped, the upper lip erect, 2-cleft, or notched, somewhat concave ; the lower lip 3-cleft and spread- ing. Stamens 4, ascending close to the upper lip, didynamous, the lower pair shorter. Anthers approximate in pairs. i. Nepeta Glech6ma, Bentham. (Gr. ; glechon, pennyroyal.) GROUND IVY. GlLL-OVER-THE-GROUND. Perennial, pubescent, creeping and trailing. Leaves round-kidney-shaped, green both sides, petioled, crenate. Corolla light blue, 2 or 3 times longer than the calyx. In damp or shady places. III. LAMIUM. Dead Nettle. (Gr. , laimos, throat, alluding to the ringent corolla.) Mostly diffuse annual or perennial herbs. Leaves commonly heart- shaped in general outline, and crenate, dentate, or entire. Flowers verticillate in axillary or terminal clusters. Calyx tubular-campanulate, with 5 equal or unequal teeth, and about 5-nerved. Tube of the corolla longer than the calyx, dilated in the throat, 2-lipped ; the upper lip con- cave and generally entire, narrowed at the base ; the lower lip spread- ing, 3-lobed, the middle lobe emarginate. Stamens 4, didynamous, close under the upper lip, approximate in pairs, the anterior pair longer. Dicotyledones. 101 i. Lamium amplexicaule, L. (L., amplexus, an encircling; caulis, stock or stem.) GREATER HENBIT or HENBIT DEAD NETTLE. Slender, ascending or decumbent annual or biennial, 6 to 18 inches long. Leaves nearly orbicular, coarsely crenate-toothed, the lower petioled, the upper sessile and clasping. Flowers purple, few and small in terminal and axillary clusters. Calyx nearly as long as the slender tube of the corolla. Upper lip of the corolla pubescent and the lower lip spotted. In fields and waste places. IV. SALVIA. Sage. (The Latin name, from salvus, safe, alluding to the healing properties.) Mostly herbs, with clustered and generally showy flowers. Calyx 2-lipped, the upper lip 3-toothed or entire, the lower 2-cleft or toothed. Corolla deeply 2-lipped, the upper lip mostly entire, straight or curved, concave ; the lower lip spreading or pendent, 3-lobed. Stamens 2, the filaments short, surmounted by long filiform connectives which bear a perfect anther-sac at their upper ends, and only a rudimentary anther- sac or none at all at their lower ends (see p. 188, Fig. 105). Style 2-cleft. Nutlets smooth. 1. Salvia lyrata, L. (Gr., lyra, lyre.) LYRE-LEAVED SAGE. Perennial or biennial, more or less pubescent or hirsute, i to 3 feet high. Basal leaves petioled, tufted, often lyre-shaped or sinuate-pinnatifid. Stem leaves sessile, narrower, often entire, and seldom more than a single pair. Flowers in loose whorls forming an interrupted raceme. Calyx campanulate, the teeth of the lower lip longer than those of the upper. Corolla blue purple, pubescent, about i inch long, upper lip short and straight, smaller than the lower lip. Both anther-cells pollen-bearing. In woods, thickets, and meadows. 2. Salvia lanceolata, Willd. (L., lanceolatus, provided with a little spear.) LANCE- LEAVED SAGE. Erect or diffuse annual, 6 to 18 inches tall, branched and very leafy. Leaves lanceolate to linear-oblong, narrowing to a petiole, sparingly serrate or entire. Flowers opposite or in interrupted, slender, spikelike racemes. Upper lip of the calyx entire, the lower 2-cleft. Corolla blue, about j inch long, the lower lip about twice as long as the upper. Lower end of the connective not anther-bearing, dilated. On our western plains. SOLANACEJE. NIGHTSHADE FAMILY. Mostly herbs, sometimes vines or shrubs, with leaves usually alter- nate and without stipules. Calyx gamosepalous, mostly 5-lobed. Corolla gamopetalous, salver-form or tubular to campanulate or rotate. Stamens generally 5, inserted on the tube of the corolla and alternate with its lobes. Corolla generally plaited in the bud. Ovary superior, IO2 Introduction to Botany. entire, 2-celled, rarely 3~5-celled. Ovules numerous on axillary pla- centae which often project prominently into the cell. Often rank-scented and poisonous. V. SOLANUM. Nightshade. (Low Latin name for nightshade.) Herbs or shrubs. Flowers mostly cymose, umbellate, or racemose, yellow, white, bluish, or purplish. Calyx campanulate or rotate, 5- toothed or cleft. Corolla rotate, 5-lobed or angled. Stamens inserted on the throat of the corolla, the anthers connate or connivant, oblong, each cell opening by a terminal pore, or by a longitudinal slit. Ovary and berry generally 2-celled. 1. Solanum Carolinense, L. HORSE NETTLE or APPLE OF SODOM. Peren- nial, green, beset with 4-8-rayed stellate hairs, and armed with straight, yellow prickles. Leaves oblong-ovate, sinuate-toothed or pinnatifid. Flowers racemose, violet or white. Lobes of the calyx lanceolate or ovate, acuminate, about half the length of the corolla. Berries orange-yellow, about f inch in diameter. In fields or waste places. 2. Solanum rostratum, Dunal. (L., restrains, beaked.) SAND BUR or TEXAS THISTLE. Annual, densely armed with awl-shaped prickles and beset with 5-8- rayed stellate hairs. Leaves deeply lobed or pinnatifid. Calyx very prickly, inclos- ing the berry. Corolla yellow, about i inch broad. One anther much exceeding the others in length and diameter. On our western prairies and in waste places. 3. Solanum Dulcamara, L. (L., dulcis, sweet; amarus, bitter.) BITTER- SWEET or NIGHTSHADE. Perennial with climbing or rambling stems, woody below. Leaves ovate or heart-shaped, the upper leaves often halberd-shaped, or with 2 leaflets or more at the base. Corolla deeply 5-cleft, violet-purple, with greenish spots at the base of the lobes. Berries red, oval or globose. In thickets or moist places. VI. LYCIUM. Matrimony Vine. (Named from the country of Lycia.) Low shrubs, or woody trailing or climbing plants, generally spiny. Leaves small, alternate, entire, often clustered on lateral spurs. Flowers solitary or clustered, purple, greenish, or white. Calyx 3-5-toothed or lobed, persisting, but not enlarging. Corolla mostly funnel-form or salver-form, 5-lobed. Stamens 5, the anthers dehiscing longitudinally. Style filiform, stigma capitate. Ovary and small, globose berry 2-celled. i. Lycium vulgare, Dunal. (L., vulgaris, common.) COMMON MATRIMONY VINE or BOX-THORN. Often somewhat spiny. Stems lithe, trailing, climbing, or recurved. Leaves oblong-spatulate or lanceolate. Flowers axillary, solitary or few-clustered on slender pedicels. Corolla funnel-form, purplish to greenish. Berry orange-red, oval. In thickets or waste places. Dicotyledones. 103 SCROPHULARIACE^E. FIGWORT FAMILY. Mostly herbs. Flowers with a 2-lipped or otherwise irregular gamo- petalous corolla and 2, 4, or 5, often didynamous stamens inserted on the corolla tube. Calyx generally 4~5-toothed or cleft. Ovary superior, 2-celled, entire or sometimes 2-lobed, ovules several to many on axillary placentae. Style simple and slender, entire or 2-lobed. I. PENTSTEMON. Beardtongue. (Gr.,jpente, five, stemon, stamen, the fifth stamen being present, though sterile.) Perennial herbs, branching from the base, with leaves usually oppo- site or verticillate, the upper sessile and often clasping. Flowers showy, white, purplish, or red, racemose or paniculate. Calyx 5-parted. Corolla mostly tubular-inflated, 2-lipped, the upper lip 2-lobed, under lip 3-lobed. Stamens 5, 4 anther-bearing and didynamous, and i sterile, either naked or bearded. Style filiform and stigma terminal. Capsule oblong to globose, containing many seeds. 1. Pentstemon pubescens, Soland. (L., pubescens, hairy.) HAIRY BEARD- TONGUE. Stems slender and pubescent, I to 3 feet high. Leaves varying from ovate and petioled below to lanceolate and sessile above. Inflorescence loose, glandular-pubescent. Beard at the base of the lower lip nearly closing the throat of the purplish to whitish corolla. Sterile filament bearded for about half its length. In dry woods or rocky grounds. 2. Pentstemon Digitalis, Nutt. (L., digitalis, finger-shaped.) FOXGLOVE BEARDTONGUE. Stem 2 to 5 feet high. Glabrous below, but inflorescence glandu- lar-pubescent. Lower leaves oblong-oval, narrowing below. Upper leaves ovate- lanceolate to lanceolate, sessile, and somewhat clasping. Corolla white, slightly 2-lipped, open in the throat, i inch or more long. Upper part of sterile filament bearded. In fields and thickets. 3. Pentstemon gracilis, Nutt. (L., gracilis, slender.) SLENDER BEARD- TONGUE. 6 to 18 inches tall, glabrous below, but the lax inflorescence glandular- pubescent. Lower leaves linear-oblong to spatula te. Upper leaves mostly linear-lanceolate. Corolla purple or whitish, \ to i inch long, tubular-funnel-form, open in the throat. Sterile filament bearded above for about of its length. On moist prairies. 4. Pentstemon Cobaea, Nutt. (From proper name, Cob6, a Spanish botanist.) COB^A BEARDTONGUE. Stems stout, i to 2 feet high, soft-pubescent beneath and glandular-pubescent above. Leaves ovate to oblong-ovate or ovate-lanceolate, often sharply dentate, the upper clasping. Corolla sometimes 2 inches long, much inflated above the middle, whitish or purplish, its lobes. about equal, rounded and spreading. Sterile filament bearded. On dry prairies. 104 Introduction to Botany. II. VERONICA. Speedwell. (Possibly named for St. Veronica.) Chiefly herbs, with opposite or sometimes alternate or verticillate leaves. Flowers usually small, inflorescence racemose, spicate, or soli- tary. Calyx mostly 4-parted, sometimes 3- or 5-parted. Corolla rotate or salver-form, generally with a 4-parted border, the upper lobe com- monly broader than the others. Stamens 2, exserted and divergent, inserted on each side of the upper lobe of the corolla. Capsule flattened, notched or obtuse at the apex, 2-celled, few- to many-seeded. Style and stigma simple. 1. Veronica officinalis, L. (L., officina, workshop.) COMMON SPEEDWELL. Pubescent. Stems ascending or prostrate, rooting at the base, 3 to 10 inches long. Leaves mostly obovate, serrate, short-petioled. Racemes spikelike and many- flowered. Flowers pale blue, about \ inch broad. Capsule much flattened and broadly notched. Perennial. In dry fields and open woods. 2. Veronica serpyllif61ia, L. (L., serpyllum, wild thyme; folium, leaf.) THYME-LEAVED SPEEDWELL. Perennial. Glabrous or softly pubescent. De- cumbent at the base, much branched, the branches ascending or erect, 2 to 10 inches high. Leaves mostly petioled, oblong, oval or ovate, crenate, those of the inflorescence lanceolate. Inflorescence a terminal, spicate, loose-flowered raceme. Corolla pale blue with dark stripes, or white, about g inch broad. Capsule broader than long, obcordate, or emarginate. Roadsides, fields, and thickets. 3. Veronica peregrina, L. (L. ( peregrinus, foreign, or exotic.) PURSLANE SPEEDWELL or NECKWEED. Nearly smooth or glandular-puberulent annual. Erect or ascending, 3 to 12 inches high. Lowest leaves oval-oblong, short-petioled, or sessile, toothed, thickish. Upper leaves mostly oblong or spatulate, longer than the solitary flowers in their axils. Corolla minute, whitish. Capsule obcordate, nearly orbicular, shorter than the calyx. In moist waste and cultivated grounds. 4. Veronica arvensis, L. (L., arvum, a field.) CORN or WALL SPEEDWELL. Slender, pubescent annual, simple or diffusely branched, 3 to 10 inches tall. Lowest leaves petioled, ovate, and crenate. Upper leaves ovate to lanceolate, frequently alternate and entire with a minute blue or nearly white flower on a short pedicel in the axil of each. Capsule minute, broadly obovate or obcordate. In cultivated grounds, fields, woods, or waste places. HI. CASTILLEIA. Painted Cup. (Named for Castillejo, Spanish botanist.) Herbs. Parasitic on the roots of other plants. Leaves alternate, entire or cut-lobed. Flowers red, purple, white, or yellow, in leafy bracted spikes, the bracts being often expanded and more brightly col- ored than the flowers. Calyx tubular, somewhat compressed laterally, Dicotyledones. 105 cleft on the upper and sometimes on the lower side. Corolla 2-lipped, the upper lip elongated, compressed laterally, sometimes curved and keeled ; the lower lip short and 3-lobed. Stamens 4, didynamous, in- closed in the upper lip of the corolla. Capsule many-seeded; style filiform, and stigma entire or 2-lobed. 1. Castilleia coccinea, Sprang. (L., coccineus, of a scarlet color.) SCARLET PAINTED CUP or INDIAN PAINT-BRUSH. Slender annual or biennial, i to 2 feet high, villous-pubescent. Basal leaves tufted, obovate or oblong, mostly entire. Stem leaves 3-5-cleft into linear or lanceolate segments. Bracts of the inflorescence brilliant scarlet, or rarely yellow. Corolla greenish yellow, its tube included within the 2-cleft calyx. In low meadows and moist thickets. 2. Castilleia sessiliflora, Pursh. (L., sessilis, low-growing ; flos, floris, flower.) DOWNY PAINTED CUP. Densely leaved perennial, 6 to 15 inches tall, clothed with a fine cinereous pubescence. Lower leaves commonly linear and entire, the upper deeply cleft into narrow, entire, or cleft lobes. Bracts of the inflorescence not bril- liantly colored, green. Lobes of the calyx linear-lanceolate. Corolla yellowish, nearly 2 inches long, its lower lip narrowly lobed. On prairies. IV. PEDICULARIS. Lousewort. (L.,pediCTtlus, louse; application not evident.) Herbs, with pinnately-lobed, cleft, or divided leaves, mostly lanceolate or linear in general outline. Flowers in terminal spikes or spicate racemes. Calyx tubular, variously cleft or toothed. Corolla 2-lipped, with cylindric tube ; the upper lip laterally flattened, curved, and some- times beaked ; lower lip erect, with 3 spreading lobes. Stamens 4, didynamous, within the upper lip ; anther-sacs equal. Capsule ovate or lanceolate, generally oblique, several-seeded. i. Pedicularis Canadensis, L. WOOD BETONY or LOUSEWORT. Hairy perennial with generally clustered stems 6 to 18 inches high. Lower leaves oblong, slender-petioled, pinnately-lobed or parted, the lobes variously toothed. Flowers in short spikes which become elongated in fruit. Calyx cleft on the lower side. Corolla usually greenish yellow or purplish, about 5 inch long; upper lip arched, with 2 minute teeth near the apex. Capsule lanceolate and flat. On banks and in thickets. LENTIBULARIACE^. BLADDERWORT FAMILY. Herbs, growing in water or in wet places, either floating or rooted. Flowers irregular, solitary or racemose, borne on erect scapes. Calyx 2-lipped. Corolla 2-lipped and personate, the upper lip usually erect and concave; lower lip 3-lobed, spreading, forming a nectariferous spur below. Stamens 2, with confluent anther-sacs. Ovary superior, io6 Introduction to Botany. i -celled, with numerous ovules on a free, central placenta. Stigma 1-2- lipped, either sessile or borne on a short style. Capsules bursting irregularly or dehiscing by valves. I. UTRICULARIA. Bladderwort. (L., utriculus, a little bladder.) Herbs, either floating free or rooted, the aquatic species having finely dissected leaves bearing numerous small bladders which are bristled at the orifice. Flowers few or solitary on slender scapes, prominently personate. (See Fig. 73, p. 145.) 1. Utricularia vulgaris, L. (L., vulgaris, common.) GREATER BLADDER- WORT or HOODED WATER MILFOIL. Floating free, the branches becoming some- times i foot long. Scapes 3 to 14 inches high with few or no scales. Divisions of the leaves capillary, bearing numerous bladders. Racemes 3-20- flowered. Corolla yellow, about \ inch broad, the spur conic and somewhat curved, shorter than the slightly 3-lobed lower lip. Pedicels recurved in fruit. In ponds and slow streams. 2. Utricularia minor, L. (L., minor, smaller.) LESSER BLADDERWORT. Floating free. Leaves scattered, dichotomously branched into a few setaceous divisions. Bladders among the leaves, few and often none. Scapes slender, 3 to 7 inches high, bearing i-io flowers. Corolla pale yellow, \ inch broad or less. Spur very much reduced, or hardly apparent. Pedicels recurved in fruit. In bogs and shallow ponds. OROBANCHACE^. BROOM RAPE FAMILY. Root parasites, from nearly white to brownish or purplish, with leaves reduced to scales, and irregular, perfect flowers, which are ses- sile in spikes or peduncled and solitary in the axils of scales. Calyx gamosepalous, 4-5-toothed or cleft, sometimes divided on one or both sides. Corolla gamopetalous, more or less 2-lipped, the upper lip 2- lobed or entire, lower lip 3-lobed ; throat of the tubular corolla ringent. Stamens 4, didynamous, alternate with the lobes of the corolla and inserted on its tube. Ovary superior and i-celled, with numerous ovules -on 2-4-parietal placentae. Capsule i -celled and 2-valved. I. APHYLLON. Naked Broomrape. (Gr., a, without; phyllon, leaf.) Brownish or whitish herbs. Scapes naked. Flowers purplish or whitish on long, glandular-pubescent peduncles. Calyx campanulate, about equally 5-cleft. Corolla somewhat 2-lipped, the upper lip 2-lobed and the lower 3-lobed. Stamens included. The 4 placentas equidistant or grouped in pairs. Dicotyledones. 107 1. Aphyllon unifldrum, Gray. (L., unus, one; flos, floris, flower.) ONE- FLOWERED BROOMRAPE or CANCER ROOT. Stem hardly appearing above the ground, and sending up i-flowered, scapelike peduncles, 3 to 8 inches high. Calyx less than 5 the length of the corolla, its divisions awl-shaped. Corolla about i inch long, white to violet, its lobes obovate and short, and tube slightly curved. Placentae equidistant. In damp woods, on the roots of various plants. 2. Aphyllon fasciculatum, Gray. (L., fasciculus, a small bundle.) CLUS- TERED BROOMRAPE or CANCER ROOT. Stems 2 to 4 inches high, glandular- pubescent, bearing 3 to 15 i-flowered peduncles. Corolla purplish yellow, plainly 2-lipped. In sandy soil, parasitizing the roots of various plants. n. CONOPHOLIS. Squaw Root or Cancer Root. (Gr., konos, cone; pholis, scale.) Light brown, scaly herb, parasitic on the roots of trees. Flowers in dense, scaly spikes. Calyx irregularly 5-toothed, split down the lower side, subtended by 2 bractlets. Corolla 2-lipped, its tube slightly curved ; upper lip nearly erect, concave, notched at the summit ; lower lip shorter, 3-lobed and spreading. Stamens exserted ; anthers pubes- cent. The 4 placentae about equidistant. i. Conopholis Americana, Wallr. SQUAW ROOT. Stems usually clustered, 3 to 10 inches high, light brown, covered with overlapping scales, lower scales much shorter than the upper. Flowers about \ inch long; corolla pale yellow. Among fallen leaves in rich woods. BIGNONIACE^E. BIGNONIA or TRUMPET CREEPER FAMILY. Shrubs or trees or woody vines. Leaves generally opposite. Flowers large, clustered, more or less irregular. Calyx 2-lipped, 5 -cleft, or entire. Corolla gamopetalous, more or less funnel-form, tubular, or campanulate, sometimes 2-lipped. Anther-bearing stamens, 2 or 4 and didynamous, alternate with the lobes of the corolla and inserted on its tube. Ovary superior, often 2-celled by ingrowth of the placentas or projections from them ; many-ovuled. Fruit, a dry capsule. Seeds flat and winged. I. BIGNONIA. Cross Vine or Tendriled Trumpet Flower. (Named for Abte Bignon.) Tall, woody climber, with compound leaves ending in a tendril. Calyx short, somewhat 5-toothed or undulate. Corolla gamopetalous, inflated above the calyx, 5-lobed, somewhat 2-lipped. Perfect stamens 4, didynamous, included. Capsule linear, flattened parallel with the partition. Seeds transversely winged. io8 Introduction to Botany. i. Bignonia capreolata, L. (L., capreolus, small tendril.) CROSS VINE. Leaves long-petioled, 2-foliate, ending with a tendril; leaflets oblong-ovate. Corolla 2 inches long, orange-red, puberulent without, yellow on the inside. Pod about 6 inches long. II. CATALPA. Catalpa or Indian Bean or Candle Tree. (The aboriginal Indian name.) Trees or sometimes shrubs, with mostly opposite, simple, petioled, ovate, or cordate leaves and showy white or mottled flowers. Tube of the corolla much swollen, its limb 5-lobed and 2-lipped. Perfect sta- mens 2, or sometimes 4. Capsule cylindric, long and slender, 2-celled. Seeds flat, with lateral wings fringed on the border. 1. Catalpa Bignonioides, Walt. (From proper name Bignon, and Gr., eidos, form.) CATALPA. Tree with thin bark. Leaves mostly broadly ovate and entire, acute or acuminate, strong scented. Corolla much spotted within, the lower lobe entire. Often planted for shade tree. In woods in the Gulf States. 2. Catalpa speciosa, Warder. (L., speciosus, showy.) CATALPA. Tree with thick and rough bark. Leaves much as in the last species, but without strong scent. Corolla little mottled within, the lower lobe emarginate. In rich woods. Often planted. ACANTHACE-ffi. ACANTHUS FAMILY. Mostly herbs, with opposite, simple leaves and regular, or only slightly irregular, perfect flowers. Calyx 4~5~parted or cleft, persistent. The gamopetalous corolla 5-lobed, nearly regular, or somewhat 2-lipped. Perfect stamens 4, and didynamous, or only 2. Ovary superior, 2-celled, with 2-1 o ovules in each cavity. Seeds borne on curved projections from the placentae. Capsule 2-celled, opening elastically by 2 valves on drying. I. RUELLIA. (Named for John Ruelle, herbalist.) Perennial herbs or shrubs, with entire, or rarely dentate, leaves and large, solitary or clustered flowers in the axils of the leaves, or terminal. Calyx 5-cleft or parted. Corolla funnel-form or salver-form, with large, spreading border. Stamens 4. Ovules 3-10 in each cavity of the ovary. Style recurved toward the apex. i. Ruellia strepens, L. (L., strepens, murmuring ; application not evident.) SMOOTH RUELLIA. Smooth or slightly pubescent perennial, i to 4 feet high. Leaves oblong-ovate or oval on short petioles. Flowers solitary or clustered in the axils. Divisions of the calyx linear-lanceolate. Corolla blue, about i| to 2 Dicotyledones. 109 inches long, the diameter of the corolla about equaling the tube. Capsule longer than or equaling the calyx. In rich soil or dry woods. 2. Ruellia ciliosa, Pursh. (L., cilium, an eye-lash.) HAIRY RUELLIA. Rather stout, i to 2| feet high, beset with soft, whitish hairs. Leaves oval or ovate- oblong, sessile or short-petioled. Flowers solitary or clustered in the axils. Corolla blue to violet-purple, its tube i to 2 inches long. Capsule shorter than the calyx. In dry soil. II. DIANTHERA. Water Willow. (Gr., dis, double; anther a, anther, alluding to the separated anther cells.) Mostly perennial herbs, growing in wet places. Leaves opposite and entire. Flowers very irregular, purplish, in axillary, peduncled spikes or heads. Calyx 5-parted ; corolla 2-lipped, the upper lip erect, concave, 2-toothed ; lower lip spreading and 3-cleft. Stamens 2, inserted on the throat of the corolla. Each cavity of the ovary containing 2 ovules. i. Dianthera Americana, L. DENSE-FLOWERED WATER WILLOW. Erect, smooth perennial, i to 2 feet high, with lanceolate or linear-lanceolate leaves. Flowers violet to nearly white, in short, long-peduncled spikes. Tube of the corolla shorter than the lips. In water and wet places. PLANTAGINACE^J. PLANTAIN FAMILY. Chiefly acaulescent or short-stemmed annuals or perennials. Leaves mainly basal, with prominent parallel ribs. Flowers chiefly in spikes or heads on long scapes. Calyx 4-parted. Corolla 4-lobed, membra- naceous. Stamens mostly 4, inserted on the tube of the corolla and alternate with its lobes. Ovary superior, i-2-celled, or falsely 3-4- celled, with i -several ovules in each cavity. I. PLANTAGO. Plantain. (The Latin name.) Short-stemmed or acaulescent herbs, with mostly prominently ribbed leaves and greenish or purplish flowers in spikes on slender scapes. Calyx of 4 membranous-margined sepals, persistent. Corolla salver- form or rotate, 4-parted, withering on the pod. Stamens mostly 4, sometimes 2, exserted. Ovary generally 2-celled, with I or more ovules in each cell. Capsule with circumscissile clehiscence. i. Plantago major, L. (L., major, larger.) COMMON or GREATER PLAN- TAIN. Perennial. Scapes sometimes becoming 2 feet tall, longer than the leaves. Spikes dense, linear-cylindric. Withered corolla not closing over the capsule in fruit. Leaves on long petioles, mostly ovate, with 3 to n ribs, which remain free no Introduction to Botany. to the base. Flowers proterogynous, stamens 4. Capsule about twice the length of the calyx. Seeds, several in the capsule. In yards and waste places. 2. Plantago lanceolata, L. (L., lanceolatus , armed with a little lance.) RIB- GRASS or ENGLISH PLANTAIN. Somewhat hairy perennial or biennial, with oblong- lanceolate leaves tapering to a petiole; ribs of the leaves 3-5, free to the base. Scapes exceeding the leaves, becoming sometimes 2 feet tall. Spikes at first short and dense, becoming later cylindric. Sepals with green midrib, and scarious on the margins. Capsule 2-seeded, somewhat longer than the calyx. In fields and waste places. 3. Plantago cordata, Lam. (L., cordatus, heart-shaped.) HEART-LEAVED or WATER PLANTAIN. Glabrous perennial. Leaves ovate to orbicular, pinnately veined, cordate or abruptly narrowed at the base, long-petioled. Scapes exceeding the leaves ; spikes becoming loosely flowered. Bracts fleshy. Capsule 2~4-seeded. Found in swampy places and along streams. 4. Plantago Piirshii, R. & S. (Latin genitive of proper name.) PURSH'S PLANTAIN. (Plantago Patagonica, var. gnaphalioides , in Gray's " Manual.") Woolly or hairy annual, with slender scapes and linear leaves. Spikes dense, cylindric, and very woolly; bracts equaling or only slightly exceeding the flowers. Capsule 2-seeded, but little exceeding the calyx. On dry prairies. 5. Plantago aristata, Michx. (L., aristatus, having ears.) LARGE-BRACTED PLANTAIN. Villous or glabrate annual, with linear leaves and dense, cylindric, pubescent, but not woolly spikes. Bracts of the inflorescence linear, ascending, many times exceeding the flowers. On dry plains or prairies. RUBIACEJE. MADDER FAMILY. Herbs or shrubs, with leaves opposite or verticillate, often connected by intermediate stipules. Flowers perfect, but sometimes dimorphous. Calyx coherent with the ovary. Corolla gamopetalous, 4~5-lobed. Sta- mens as many as the lobes of the corolla and inserted on its tube, alter- nate with the lobes. Ovary 2-4-celled, with ovules solitary or many in each cavity. Fruit various. I. HOUSTONIA. Bluets. (Named for Dr. William Houston, English botanist.) Mostly tufted, erect or spreading herbs, with opposite and entire, sometimes ciliate leaves, and commonly dimorphous, blue, purple, or white flowers. Calyx 4-lobed, corolla funnel-form or salver-form, 4-lobed. Stamens 4. Ovary 2-celled, with several ovules in each cell. Style slender; stigmas 2. i. Houstonia coerulea, L. (L., cceruleus, azure.) BLUETS or INNOCENCE. Smooth, with erect and slender stems sparingly branched from the base, 3 to 7 inches high. Lower leaves spatulate or oblanceolate ; upper leaves oblong-elliptic, Dicotyledones. 1 1 1 about J inch long. Peduncles slender, i inch or more long. Corolla light blue to nearly white, with yellow center, j to 5 inch broad. Perennial by slender rootstock. In grassy or moist places. 2. Houstonia minima, Beck. (L., minimus, smallest.) LEAST BLUETS. Diffuse or spreading, and generally rough, annual, i to z\ inches high. Lower leaves spatulate or ovate, upper leaves oblong-elliptic to nearly linear. Peduncles i inch or less long. Calyx lobes rather broad and much exceeding the capsule. Corolla violet to purple. In dry soil. 3. Houstonia purpurea, L. (L., purpureus, purple.) LARGE HOUSTONIA. Erect and stout, mostly glabrous perennial, 4 to 18 inches high. Leaves ovate or ovate-lanceolate, sometimes 2 inches long. Flowers in terminal cymes or cymose clusters. Corolla funnel-form, lilac or purple. Calyx lobes longer than the globular pod. In woodlands or open places. 4. Houstonia ciliolata, Torr. (L.,ci/ium, an eye-lash.) FRINGED HOUSTONIA. Tufted, erect perennial, 4 to 7 inches tall. Leaves oblanceolate to obovate, ciliate- fringed. Corolla purple or lilac. On rocky banks. 5. Houstonia angustifolia, Michx. (L., angustus, narrow; folium, leaf.) NARROW- LEAVED HOUSTONIA. Stiff, erect, glabrous perennial, rising i to 2 feet from a deep root. Leaves mostly linear, often in fascicled clusters. Flowers on short pedicels in dense, terminal, cymose clusters. Corolla purplish to white, its lobes bearded within. Capsule compressed-obovoid, nearly as long as the calyx lobes. In open places. n. MITCHELLA. Partridge Berry. (Named for Dr. John Mitchell, botanist.) Creeping herbs, with opposite, evergreen leaves and terminal, dimor- phous flowers in pairs, with united ovaries. Calyx usually 4-toothed. Corolla funnel-form and 4-lobed. Stamens 4, inserted on the throat of the corolla alternate with its lobes. Ovary 4-celled, with i ovule in each cavity. Style exserted ; stigmas 4. Flowers white or tinged with purple, fragrant. Fruit, 2 united, scarlet, edible drupes. i. Mitchella repens, L. (L., repens, creeping or trailing.) PARTRIDGE- BERRY or TWIN-BERRY. Stems slender and rooting at the nodes. Leaves peti- oled, rounded-ovate, sometimes variegated with white lines. Flowers white and sessile. Corolla about \ inch long. Fruit persisting through the winter. At the bases of trees in dry woods. HI. GALIUM. Bedstraw or Cleavers. (Gr.,gaZa, milk, which some species have the property of curdling.) Slender herbs, with square stems and whorled leaves, and small flowers in axillary or terminal cymose clusters. Tube of the calyx some- what globose, its teeth minute or none. Corolla rotate, mostly 4-parted. H2 Introduction to Botany. Stamens 4, or sometimes 3, exserted. Ovary 2-celled with i ovule in each cavity. Fruit separating into 2 i-seeded carpels. 1. Galium Aparine, L. (Gr., aparine, goose-grass.) CLEAVERS or GOOSE- GRASS. Weak annual ; the stem becoming 2 to 5 feet long, beset with backward- growing bristles. Leaves lanceolate or oblanceolate, i to 3 inches long, about 8 in a whorl, rough on margins and midrib. Flowers white, 1-3 in the axils. In shaded grounds, or habitat various. 2. Galium circaezans, Michx. WILD LIQUORICE. Somewhat pubescent perennial, i to 2 feet high. Leaves ovate to oval-lanceolate, 4 in a whorl. Pe- duncles forked ; corolla greenish, hairy outside. In dry woods. CAPRIFOLIACE^. HONEYSUCKLE FAMILY. Shrubs and woody vines, or sometimes herbs, with opposite, exstip- ulate leaves. Calyx 3~5-toothed or lobed, its tube coherent with the ovary. Corolla gamopetalous, rotate to tubular. Stamens 5, or some- times 4, inserted on the tube of the corolla alternate with its lobes. Ovary i-6-celled. Fruit a berry, drupe, or capsule. I. SAMBUCUS. Elder. (The Latin name.) Shrubs, with pinnate leaves and serrate or laciniate leaflets, and small, white flowers in dense, compound cymes. Calyx tube 3~5-toothed or lobed. Corolla somewhat campanulate, 3~5-lobed. Stamens 5, in- serted on the base of the corolla. Ovary 3-5-celled. Stigmas 3. Fruit a small, berrylike, juicy drupe. 1. Sambucus Canadensis, L. COMMON ELDER. Nearly glabrous, 3 to 10 feet high. Younger stems with large, white pith. Leaflets 5-11, ovate or oval, ser- rate, acuminate. Cymes broad and flat. Fruit purple to black. Usually in moist soil. 2. Sambucus racemosa, L. (L., racemosus, full of clusters.) RED-BERRIED ELDER. 2 to 12 feet high, with commonly pubescent twigs and leaves, and warty bark. Leaflets 5-7, ovate-lanceolate, sharply serrate. Cymes somewhat pyramidal. Fruit bright red. In rocky places. H. VIBURNUM. (The Latin name.) Shrubs or trees, with simple leaves and mostly white flowers in com- pound cymes. Calyx 5-toothed. Corolla deeply 5-lobed, spreading. Stamens 5, inserted on the tube of the corolla, exserted. Ovary in- Dicotyledones. 113 ferior, i-3-celled, with a single ovule in each cell. Style short ; stigmas 1-3. Fruit a i-celled, i-seeded drupe. 1. Viburnum Opulus, L. (L., opulus, a kind of maple.) CRANBERRY-TREE or HiGH-BUSH CRANBERRY. Shrub, becoming sometimes 12 feet high. Branches upright and smooth. Leaves deeply 3-lobed toward the apex, the lobes dentate. Marginal flowers much larger than the others. Drupe globose, red, acid. In low ground along streams. 2. Viburnum pubescens, Pursh. DOWNY-LEAVED ARROW-WOOD. Low branching shrub, 2 to 5 feet high. Leaves ovate, coarsely serrate, nearly sessile, acute, soft-pubescent beneath. All the flowers perfect. Drupes oval and nearly black. In rocky woods. 3. Viburnum prunifolium, L. (L,.,prunus, plum; folium, leaf.) BLACK HAW, STAG- BUSH, or SLOE. Shrub or small tree, with ovate or oval, finely serrate leaves, 1 to 3 inches long, obtuse at the apex. Cymes compound and sessile. Petioles hardly or not at all margined. Fruit ripening in the fall, oval, bluish black, sweet. In dry or moist soil. 4. Viburnum Lentago, L. NANNY-BERRY, SHEEP-BERRY, or SWEET VIBUR- NUM. Shrub or small tree with ovate, finely serrate leaves, acuminate at the apex, 2 to 4 inches long ; petioles long and often margined. Drupes oval, bluish black, with a bloom. Cymes compound and sessile. Along banks of streams and in woods. HI. TRIOSTEUM. (Abbreviation of triostesspermum, from Gr., tri, three; osteon, bone; sperma, seed; alluding to the three bony seeds.) Perennial herbs, with opposite leaves much narrowed below the middle, sessile and connate around the stem. Flowers axillary, sessile, solitary or clustered. Calyx with 5 linear-lanceolate lobes, its tube ovoid. Corolla but little longer than the calyx, 5-lobed, its tube cam- panulate or tubular, swollen at the base. Stamens 5, inserted on the corolla tube. Ovary generally 3-celled with i ovule in each cavity. Style slender ; stigma 3-5-lobed. Fruit an orange or red drupe, con- taining bony nutlets. 1. Triosteum perfoliatum, L. (L., per, through ; folium, leaf.) FEVER-WORT or HORSE-GENTIAN. Stems stout, 2 to 4 feet high, beset with soft hairs. Leaves oval, abruptly constricted below the middle, 4 to 9 inches long. Flowers brownish purple, clustered in the axils of the leaves. Drupes orange-color. In rich soil. 2. Triosteum angustif61ium, L. (L., angustus, narrow; folium, leaf.) YEL- LOW or NARROW-LEAVED HORSE-GENTIAN. Stems more slender than in the preceding species, bristly hairy, i to 3 feet tall. Leaves lanceolate, tapering below the middle, 3 to 5 inches long. Flowers pale greenish yellow, usually solitary in the axils. In shady situations. 1 14 Introduction to Botany. IV. LONICERA. Honeysuckle or Woodbine. (Latinized form of Lonitzer, German herbalist.) Erect or climbing shrubs, with opposite, entire, sometimes perfoliate leaves. Flowers in clusters, or sometimes solitary. Calyx nearly globular, slightly 5-toothed. Corolla tubular or funnel-form, more or less irregularly 5-lobed. Stamens 5, inserted on the tube of the corolla. Ovary 2-3-celled, with numerous ovules in each cavity. Style slender and stigma capitate ; berry fleshy. 1. Lonicera Sullivantii, Gray. (Latin genitive of proper name.) SULLI- VANT'S HONEYSUCKLE. Smooth and glaucus, 3 to 6 feet long. Leaves oval or obovate, glaucus, and often pubescent beneath. Corolla pale yellow, hairy within, its tube about | inch long. Filaments nearly glabrous. In woods. 2. Lonicera sempervirens, L. (L., semper, always; virens, growing green.) TRUMPET or CORAL HONEYSUCKLE. Climbing high. Leaves oval, the upper- most connate-perfoliate, dark green above, glaucus beneath. Flowers in whorls in terminal, interrupted spikes. Corolla scarlet outside, yellow inside, and sometimes yellow throughout, from i to 1$ inches long, trumpet-shaped. Berries scarlet. Common in cultivation. In copses, or habitat various. VALERIANACEJE. VALERIAN FAMILY. Herbs, with opposite, exstipulate leaves, and small, more or less irregular flowers in forked or panicled cymes. Calyx tube adherent to the ovary, its limb nearly or quite wanting, often becoming prominent in the fruit. Corolla tubular or funnel-form, mostly 5-lobed, and sometimes irregular. Stamens 1-4, inserted on the tube of the corolla alternate with its lobes, mostly exserted. Ovary inferior, i-3-celled ; i cell con- taining a single ovule and the others empty. Style slender ; stigmas 1-3. Fruit dry and indehiscent. I. VALERIAN A. Valerian. (Latin name of unknown origin.) Perennial, mostly tall herbs with thickened, strong-scented roots, and paniculate, cymose flowers. Limb of the calyx divided into several plumose bristles which are inrolled in the flower, but straighten out and become conspicuous in the fruit. The funnel-form or tubular corolla gibbous near the base and nearly regularly 5-lobed above. Stamens mostly 3. Fruit i -celled and seedlike. i. Valeriana pauciflbra, Michx. (L.,paucus, few; flos,fioris, flower.) LARGE- Dicotyledones. 115 FLOWERED VALERIAN. Stem smooth, erect or ascending, i to 3 feet high. Base leaves cordate or ovate, stem leaves with 3-7 ovate leaflets. Divisions of the pani- cled cyme few-flowered. Corolla pale pink, its tube inch or more long. In moist soil. 2. Valeriana edulis, Nutt. (L., edulis, edible.) EDIBLE VALERIAN. Smooth or finely pubescent, erect, i to 4 feet high from a deep, fusiform root. Basal leaves spatulate to lanceolate. Stem leaves pinnately 3~7-parted into linear or lanceolate segments. Inflorescence an elongate, interrupted panicle. Flowers small, yellow- ish white, nearly dioecious. On moist prairies. II. VALERIANELLA. Corn Salad or Lamb-lettuce. (Name a diminutive of Valerian.) Annuals or biennials, mostly glabrous, and dichotorhously branched. Leaves tender and succulent, those of the base tufted, entire ; the stem leaves often dentate. Limb of the calyx obsolete or short and toothed. Corolla funnel-form or tubular, equally or unequally 5-lobed, small, and white or whitish. Stamens 3. Style slightly 3-lobed. Fruit 3-celled, 2 cells empty and the third containing a single seed. Inflorescence a corymbed or panicled cyme. 1. Valerianella chenopodifolia, DC. (Gr., chen, goose; pou, foot; folium, leaf.) GOOSE-FOOT CORN SALAD. Smooth, i to 2 feet high. Lower leaves broadly spatulate, somewhat repand, stem leaves oblong-oval to lanceolate. Cymes inch or more broad. Flowers very small, white; fruit triangular-pyramidal in form. In moist soil. 2. Valerianella radiata, Dufr. (L., radiatus, provided with spokes or rays.) BEAKED CORN SALAD. Nearly or quite glabrous, 6 to 18 inches high. Lower leaves spatulate or oblong-oval, entire ; upper leaves oblong-elliptic to lanceolate, often dentate. Cymes about 5 inch broad or less. Flowers white and very small. Fruit tetragonal, broadly grooved, oblong or ovoid, mostly downy pubescent. In moist soil. 3. Valerianella stenocarpa, Krok. (Gr. stenos, narrow'; karpos, fruit.) NARROW-CELLED CORN SALAD. Similar in general aspect to the preceding species, but the fruit commonly glabrous, sometimes downy-pubescent, and the grooves narrow. In moist soil. CAMPANULACEJE. BELLFLOWER FAMILY. Herbs, mostly with a milky juice, alternate, exstipulate leaves, and solitary or scattered flowers. Calyx tube adherent to the ovary, its limb mostly 5-lobed or parted. Corolla gamopetalous, 5-lobed, its tube sometimes parted down one side. Stamens 5, inserted with the corolla and alternate with its lobes. Ovary generally 2-5-celled with axillary placenta? ; or sometimes i -celled with 2 parietal placentae. Style simple n6 Introduction to Botany. with a tuft of hairs above ; stigma generally 2-5-lobed. Fruit a capsule or berry with many small seeds. I. SPECULARIA. Venus's Looking-glass. (L., Specularia, a window glass made of talc; from bluish color of the flowers.) Low annuals, with alternate leaves and axillary blue or purplish flowers ; the earlier flowers small and cleistogamous. Calyx 5-, or sometimes 3~4-lobed. Corolla wheel-shaped, 5-lobed. Stamens 5, with membranous, hairy filaments. Ovary mostly 3-celled ; sometimes 2- or 4-celled. Stigma usually 3-lobed. Capsule opening by lateral valves. 1. Specularia perfoliata, A. DC. (L., per, through; folium, leaf.) Some- what pubescent, 6 to 20 inches tall. Leaves rounded, crenate-dentate, cordate and clasping at the base. Flowers solitary, or few together in the axils, sessile. The upper and older flowers with an expanded and conspicuous corolla, blue or violet. In open grounds or dry woods. 2. Specularia leptocarpa, Gray. (Gr. leptos, small; karpos, fruit.) Simple or branched, 6 to 15 inches high. Leaves lanceolate, with mostly solitary sessile flowers in the axils. Calyx lobes 4-5, awl-shaped, but in the earlier flowers only 3. Corolla of the earlier flowers rudimentary, of the later flowers rotate, 3 inch or more broad. Capsule nearly cylindrical. In dry soil. COMPO'SITJE. COMPOSITE FAMILY. Flowers in a compact head, borne on an enlarged common receptacle, the head having the appearance of a double flower. Many bracts sub- tend the head, forming an involucre somewhat simulating a calyx. Limb of the calyx (termed pappus in this family), rising from near the summit of the I -celled ovary in the form of bristles, awns, scales, or teeth, or in the form of a cup, or sometimes entirely absent. Corolla strap-shaped, or tubular, mostly 5-lobed. Stamens 5, rarely 4, inserted on the tube of the corolla ; anthers united into a tube around the style. Ovary i-celled and i-seeded; style 2-cleft. Fruit a dry, i-seeded achene. Heads which are composed of strap-shaped (ligulate) corollas throughout, or only at the margin, are termed radiate, flowers with ligu- late corollas being termed ray flowers. Heads without ray flowers are termed discoid. The family is divided into two series or suborders : I. TubuliflorcB) in which the corollas are all tubular; or ligulate only at the margin of the head, where they are pistillate, or neutral. II. Ligitti- flora, in which the corollas are ligulate in all flowers of the head, and all of the flowers are perfect. Frequently bracts, in this family called chaff, Dicotyledones. 117 occur on the receptacle among the flowers. The receptacle is said to be naked when these are absent. A. Corollas all tubular, or ligulate and pistillate, or neutral only, at the margin of the head. Flowers of the head all tubular; dioecious. ANTENNARIA II. Disk flowers tubular; ray flowers ligulate. Ray flowers white, pink, or purple, rarely yellow. Pappus of capillary bristles. Ray flowers numerous and pistillate; bracts of the involucre little im- bricated; receptacle naked. ERIGERON I. Pappus a minute crown or wanting. (a) Ray flowers pistillate or neutral ; bracts of the involucre imbricated in several rows; receptacle convex and chaffy near the summit; heads on long, terminal peduncles. ANTHEMIS III. (6) Ray flowers pistillate; bracts of the involucre imbricated in few rows, appressed; receptacle chaffy; heads small in corymbose clusters. ACHILLEA IV. (c~) Ray flowers pistillate; disk flowers with flattened tubes; involucral scales imbricated in several rows; receptacle without chaff; heads large on long peduncles. CHRYSANTHEMUM V. Ray flowers yellow. Pappus of capillary bristles; disk flowers as well as ray flowers, when present, yellow. SENECIO VI. B. Corollas all ligulate, and all flowers of the head perfect. Heads borne singly on a scape. (a) Leaves tufted at the base, entire. TROXIMON VII. (b) Leaves tufted at the base, pinnatifid or runcinate. TARAXACUM VIII. Heads borne on long, bracted peduncles, sometimes scapose. PYRRHOPAPPUS IX. Heads in corymbose or paniculate clusters on leafy stems; leaves with prickly margins. SONCHUS X. I. Tubuliflora. I. ERIGERON. Fleabane. (Gr., eri, early; geron, old man, from the hoariness of some of the early spring species.) Heads radiate on the margin. Ray flowers white, pinkish, or purple ; disk flowers yellow. Ray flowers numerous and pistillate. Involucre hemispheric or campanulate, its bracts narrow and little, or not at all, imbricated. Receptacle naked, nearly flat. Pappus a row of capil- lary bristles with smaller ones interspersed. Achenes flattened, often pubescent and 2-nerved. i. Erigeron annuus, Pers. (L., annuus, annual.) SWEET SCABIOUS. Slightly pubescent annuals, i to 4 feet high, corymbosely branched above. Lower leaves petioled, ovate, or ovate-lanceolate, mostly coarsely dentate; the upper leaves lanceolate or ovate-lanceolate, sessile or short-petioled, sharply dentate. 40-70 linear, white or purplish, rays. Pappus doubled by an outer row of slender scales; the inner row of capillary bristles often wanting in the ray flowers. In fields and waste places. n8 Introduction to Botany. 2. Erigeron strigosus, Muhl. (L., strigosus, thin or narrow.) DAISY FLEA- BANE. Resembling the preceding species, but smaller, and the lower leaves oblong or spatulate, and tapering into a slender petiole; upper leaves linear-oblong or linear-lanceolate. Clothed with an appressed pubescence. Rays white, and twice the length of the puberulent involucre. In fields. 3. Erigeron bellidifolius, Muhl. (L., bellis, bellidis, the ox-eye daisy; folium, leaf.) ROBIN'S PLANTAIN. Hairy perennial, producing stolons or offsets at the base. Basal leaves tufted, obovate, or spatulate ; upper leaves few and distant, anceolate-oblong, partly clasping. Heads i to 15 inches broad on slender pedun- cles. Rays about 50, violet or purple. Pappus simple. Moist banks and copses. 4. Erigeron Philadelphicus, L. COMMON FLEABANE. Hairy or nearly gla- brous perennial, forming stolons or offsets at the base. Stems slender, i to 3 feet high. Lower leaves obovate or spatulate, dentate, tapering to a short petiole. Upper leaves oblong or lanceolate, clasping at the base. Rays 100 or more, light rose-purple. Pappus simple. In fields and woods. II. ANTENNARIA. Everlasting. (Named from resemblance of the pappus to the antennae of some insects.) Flowers of the head many, dioecious, all tubular. Corolla of the staminate flowers truncate and minutely dentate, the anthers caudate, pappus scant, club-shaped, barbed, or smooth above. Pistillate flowers with slender, tubular corolla and copious, capillary pappus, united beneath to form a ring. Involucre white or colored, and dry, the scales numerous and imbricated. Receptacle without chaff, and con- vex or flat. Perennial herbs clothed with a white wool. Leaves entire. i. Antennaria plantaginifolia, Richards. (L., plantago , plantain ; folium, leaf.) PLANTAIN LEAF or MOUSE-EAR EVERLASTING. 3 to 18 inches high, spreading by stolons. Young leaves softly woolly, becoming green above and hoary beneath. Basal leaves petioled, obovate, or broadly spatulate, 3-nerved. Stem leaves lanceo- late, appressed. Heads in corymbose clusters. Scales of the involucre white or greenish white, imbricated in about 3 rows. In dry soil or open woods. III. ANTHEMIS. Chamomile. (The ancient Greek name of the chamomile.) Heads radiate on the margins ; ray flowers white or yellow, either pistillate or neutral. Disk flowers yellow, perfect. Involucre hemi- spheric, with bracts imbricated in several rows. Receptacle convex and chaffy, at least near the summit. Pappus a minute crown or wanting. Achenes oblong and ribbed. Strong-scented annual or perennial herbs, with alternate, pinnatifid, or dissected leaves and heads usually borne on long terminal peduncles. Dicotyledones. 119 i. Anthemis Cdtula, L. (Gr., kotyle, a small measure or cup.) MAYWEED or DOG FENNEL. Strong-scented and pungent annual, branched, i to 2 feet high. Leaves finely 1-3 pinnately dissected. Rays white, 10-18, neutral or with an abor- tive pistil. Pappus none. Receptacle with bristly chaff near the summit only. By roadsides or in fields and waste places. IV. ACHILLEA. Yarrow. (Named for Achilles, who is supposed to have discovered its virtues.) Heads small, with both radiate and tubular flowers, in corymbose clusters at the ends of the branches. Ray flowers white, few and fertile. Disk flowers yellow. Bracts of the involucre imbricated in a few rows, appressed. Receptacle chaffy, convex, or flattish. Pappus none. Achenes flattened and somewhat margined. Perennial herbs, with serrate, pinnatifid, or finely dissected, alternate leaves. i. Achillea Millefolium, L. (L., mille, thousand; folium, leaf.) COMMON YARROW or MILFOIL. Perennial, from a horizontal rootstock, becoming i to 2 feet high. Leaves twice pinnatifid into slender segments. Flowers in a compound, flat-topped corymb. Heads small and numerous; ray flowers 4-5, mostly white, sometimes pink or purple ; bracts of the involucre oblong, acute. Habitat various. V. CHRYSANTHEMUM. Ox-eye Daisy. (Gr., chrysanthemon, golden flower.) Heads composed of both tubular and ray flowers; the rays fertile, white, rose-colored, or yellow. Disk flowers with flattened tubes, per- fect. Scales of the involucre imbricated in several rows. Receptacle flat or convex, without chaff. Biennial, perennial, or annual herbs, with mostly large heads borne on long peduncles. i. Chrysanthemum Leucanthemum, L. (Gr., leukos, white ; anthemon, flower.) OX-EYE or WHITE DAISY. Perennial, i to 3 feet high. Branches terminated by a single large head on a long peduncle. Rays white, 20-30. Pappus none. Basal leaves petioled, spatulate, incised. Upper leaves spatulate to linear, cut-toothed, clasping at the base. Scales of the involucre with scarious and brown margins. In pastures, fields, and waste places. VI. SENECIO. Groundsel. (L., senex, old imn, from the hoariness of some species.) Heads usually consisting of both disk and ray flowers. Ray flowers, when present, pistillate ; disk flowers perfect and fertile. Both disk and ray flowers usually yellow. Pappus of numerous fine capillary bristles. I2O Introduction to Botany. Involucre of i row of bracts, subtended by a few bractlets. Receptacle flat and naked. Annual or perennial herbs, with solitary or corymbed heads. Achenes mostly cylindrical, 5-io-ribbed, downy. 1. Senecio lobatus, Pers. (Gr., lobos, lobe.) BUTTERWEED or CRESS-LEAVED GROUNDSEL. Glabrous or only slightly woolly annual, i to 3 feet high. Leaves pinnately divided, the lower ones petioled. Heads rather more than inch broad, numerous in terminal corymbs. Rays 6-10, conspicuous. Involucre nearly cylindric, usually with no smaller outer bracts. In wet grounds. 2. Senecio aureus, L. (L., aureus, golden yellow.) GOLDEN RAGWORT or SQUAW WEED. Nearly or quite glabrous perennial, i to 2^ feet high. Basal leaves long-petioled, rounded or nearly heart-shaped, crenate. Stem leaves vary- ing from lyrate below to lanceolate above, and more or less pinnatifid, sessile, and clasping. Heads of an inch or more broad, borne on slender peduncles in an open corymb. Rays 8-12, yellow. This species is quite variable. Var. obovatus, T. & G., has basal leaves round-obovate, the earliest being almost sessile and tufted. Var. Balsamitce, T. & G., has spatulate, oblong, or lanceolate basal leaves, lyrate, pinnatifid upper leaves, and heads small and numerous. In moist, open ground. II. Liguliflora. VII. TROXIMON. Perennial or annual herbs, with leaves tufted at the base, linear or lanceolate and entire. Heads of ligulate flowers large, yellow or rarely purple, borne singly at the end of a naked or sometimes bracted scape. Scales of the involucre imbricated in 2-3 rows. Receptacle flat, naked, or pitted. Achenes beaked, or sometimes beakless, lo-ribbed. Pappus of many rigid capillary bristles. 1. Troximon cuspidatum, Pursh. (L., cuspidatus, pointed.) Scape i foot high. Leaves lanceolate, elongate, and tapering, entire, woolly on the margins. Achenes beakless. Plains. 2. Troximon glaucum, Nutt. (Gr., glaukos, bluish gray.) Scape i to 2 feet high. Leaves oblong or lanceolate, entire, or sometimes dentate or pinnatifid. Heads i to 2 inches wide. Achenes prominently beaked. Plains. VIII. TARAXACUM. Dandelion. (Gr., tarasso, to disquiet, in allusion to medicinal properties.) Perennial or biennial herbs from a thickened tap-root. Heads large, many-flowered, solitary on the summit of a slender, hollow scape, which exudes a milky secretion when broken. Sca ] es of the involucre in 2 rows, the outer scales short, reflexed with age, those of the inner row Dicotyledones. 121 linear and erect. Achenes 4-5 -ribbed, prolonged into a beak bearing a copious, soft, capillary pappus. Flowers yellow. i. Taraxacum officinale, Weber. (L., officina, workshop.) COMMON DAN- DELION. Leaves pinnatifid or runcinate, clustered near the ground. Heads crowded with many golden yellow flowers. Beak bearing the pappus becoming very elongate and filiform in fruit. In pastures, fields, and yards. IX. PYRRHOPAPPUS. False Dandelion. (Gr., pyrrhos, reddish or flame-colored; pappos, pappus.) Mostly perennial herbs, with the general characteristics of the dan- delion. Large heads of yellow flowers borne 'on long and usually bracted peduncles. Pappus of a reddish color, surrounded at the base by a soft, hairy ring, and borne above the achene on an elongate beak. 1. Pyrrhopappus Carolinianus, DC. Stems branching, i to 2 feet high. Basal leaves oblong or lanceolate, entire, toothed, or pinnatifid. Upper leaves nearly lanceolate and partly clasping. .Outer bracts of the involucre awl-shaped and spreading, inner bracts erect and indurated at the apex. Beak much longer than the achene. In dry fields. 2. Pyrrhopappus scaposus. (Gr., skapos, a staff.) ROUGH FALSE DANDELION. Perennial from tuberous thickened roots. No stem leaves present. Basal leaves deeply pinnatifid. Scape often naked, or with a small basal leaf. On prairies. X. SONCHUS. Sow Thistle. (The ancient Greek name.) Coarse annual or perennial herbs, exuding a milky secretion when wounded. Leaves mostly lobed or pinnatifid, with prickly, toothed margins. Heads of yellow flowers in corymbose or paniculate clusters. Bracts of the involucre imbricated in several rows, becoming shorter toward the outside. Achenes somewhat flattened, io-2o-ribbed. Pappus of many soft and fine bristles, not borne on an elongated beak. 1. Sonchus oleraceus, L. (L., oleraceus, pertaining to vegetables.) COMMON Sow THISTLE or HARE'S LETTUCE. Annual, i to 5 feet high. Basal leaves petioled, lyrate-pinnatifid in outline. Upper leaves sessile and clasping by an auricled or sagittate base, margins with mucronate teeth. Achenes sfriate and transversely wrinkled. Flowers pale yellow. In fields and waste places. 2. Sonchus asper, Vill. (L., asper, rough.) SPINY-LEAVED Sow THISTLE. Similar in general aspect to the preceding species. Lower leaves petioled, obovate, or spatulate. Upper leaves sessile and clasping, with rounded basal lobes; the margins more rigidly spiny-toothed than in the preceding species. Achenes flattened and margined, 3-nerved on each side. In fields and waste places. INDEX TO FLORA. Acanthaceae, 108. Barberry, 43. Butterfly weed, 92. Acanthus family, 108. Barberry family, 42. Butternut, 28. Acer, 74. Barren strawberry, 61. Butterweed, 120. Achillea, 119. Basswood, 78. Actaea, 39. Bastard toadflax, 34, 35. Callirrhoe, 79. ^Esculus, 75. Beardtongue, 103. Calycocarpum, 44. Ague tree, 45. Bedstraw, 111. Cainassia, 21. Alllum, 20. Bellflower family, 115. Camelina, 52. Alyssum, 53, 54. Berberidaceae, 42. Campanulaceae, 115. Amaryllidaceae, 24. Berberis, 43. Campion, 37. Amelanchier, 63. Betula, 30. Cancer root, 107. American Black Larch, 14. Bignonia, 107, 108. Candle tree, 108. American cowslip, 90. Bignoniaceae, 107. Caprifoliaceae, "112. American ivy, 77. Bignonia family, 107. Capsella, 52. American pea vine, 68. Bilberry, 87. Cardamine, 50. Amorpha, 67. Bindweed, 93, 94. Carex, 17. Ampelopsis, 77. Birch, 30, 31. Carpinus, 31. Anacardiaceae, 73. Bitter cress, 50. Carrot family, 82. Anagallis, 89. Bittersweet, 102. Carya, 28. Androsace, 89. Blackberry, 59. Caryophyllaceae, 37. Anemone, 40. Black haw, 113. Castilleia, 104, 105. Angiospermae, 15. Black mustard, 49. Catalpa, 108. Anonaceae, 38. Black snakeroot, 84. Catchfly, 37. Anteunaria, 118. Bladder nut, 74, 75. Cat mint, 100. Anthemis, 118, 119. Bladderwort, 106. Cat-tail, 15. Aphyllon, 106, 107. Bladderwort family, 105. Caulophyllum, 48. Apple, 63. Bloodroot, 45, 46. Ceanothus, 76. Apple of Sodom, 102. Blueberry, 87, 88. Cedar, white, 14 ; red, 14. Aquilegia, 39. Blue birch, 31. Celandine poppy, 46. Arabia, 53. Blue cohosh, 43. Celtis, 34. Araceae, 18. Blue-eyed grass, 26. Centunculus, 89. Arbor vitae, 14. Blue grass, 16. Cerastium, 37. Argemone, 45. Bluets, 110, 111. Cercis, 68. Arisaema, 18 ; inflorescence Borage family, 96. Chaerophyllum, 85. of, 18. Boraginaceae, 96. Chatfweed, 89. Arrow-wood, 113. Box elder, 74. Chamomile, 118. Arum family, 18. Box-thorn, 102. Cherry, 57, 58. Asclepiadaceae, 91. Bramble, 59. Chervil, 85. Asclepias, 92. Brassica, 49. Chickweed, 37, 38. Asclepiodora, 92. Broom-rape family, 106. Chinese primrose, 88. Ash, 91. Bryophyta, 5. Chrysanthemum, 119. Asimina, 88. Buckeye, 75. Cinquefoil, 60, 61. Astragalus, 67, 68. Buckthorn, 75, 76. Claytonia, 36. Avens, 61, 62. Buckthorn family, 75. Cleavers, 111, 112. Buckwheat family, 35. Clover, 66. Baneberrv, 89- Bulbous cress, 50. Cohosh, 39. Baptisia, 65. Buttercup, 41, 42. Columbine, 39, 40. I2 3 I2 4 introduction to Botany. Comandra, 84, 35. Dutchman's breeches, 46. Gold-of-pleasure, 52. Commelinaceae, 19. Dwarf alder, 76. Gooseberry, 55. Composite, 116. Goosegrass, 112. Composite family, 116. Easter bell, 22. Gramineae, 15. Conifene, 12. Ebenaceae, 90. Grape family, 76. Conopholis, 10T. Convolvulaceae, 92. Ebony family, 90. Elder, 112. Grape, 77. Grass family, 15. Convolvulus, 93, 94. Eleocharis, 17. Grasp flower, diagram of, 16. Cornaceaa, 86. Ellisia, 96. Greater henbit, 101. Cornel, 86. Elm, 33. Greenbrier, 20. Corn salad, 115. Epigaea, 87. Green dragon, 18. Cornus, 86. Ericaceae 86. Green milkweed, 92. Corydalis, 4T. Corylus, 32. Cottonwood, 29. Cow parsnip, 83. Cowslip, 88. Crab apple, 63. Cranberry, 87. Cranberry tree, 113. Erigenia,'s5, 86. Erigeron, 117, 118. Erythronium, 22. Euphorbia, 72. Euphorbiaceae, 72. Evening primrose, 82. Evening primrose family, 81. Gromwell, 97. Ground ivy, 100. Ground laurel, 87. Ground pink, 95. Ground plum, 67, 68. Groundsel, 119. Gymnocladus, 69. Gymnospermse, 12. Cranesbill, TO. Cratsegus, 64. Cress, 49, 50. False acacia, 67. False dandelion, 121. Hackberry, 34. Hackmatack, 14. Cross vine, 107, 108. Crowfoot, 41, 42. False flax, 52. False grape, 77. Harbinger of spring, 85, 86. Hare's lettuce, 122. Crowfoot family, 38. False gromwell, 97, 98. Haw, &4. Cruciferae, 47. False indigo, 65, 67. Hawthorn, 64. Cupseed, 44. False pimpernel, 89. Hazelnut, 32. Cupuliferae, 30. False rue anemone, 39. Heart's-ease, 79, 81. Currant, 55, 56. False Solomon's seal, 23, 24. Heath family, 86. Custard-apple family, 88. Cynoglossum, 96, 97. Fever-wort, 113. Figwort family, 103. Hedge mustard, 49. Henbit, 101. Cyperaceae, 18. Filbert, 32. Hepatica, 41. Cyperus, 17. Fire pink, 37. Heracleum, 83. Cypripedium, 26. Five-finger, 60, 61. Hickory, 28. Fleabane, 117, 118. Honey locust, 69. Daisy, 119. Flower-de-luce, 25. Honeysuckle, 114. Dandelion, 120. Date plum, 90. Four o'clock family, 36. Foxglove beardtongue, 103. Honeysuckle family, 112. Hop hornbeam, 31, 32. Dead nettle, 100, 101. Fragaria, 60. Hornbeam, 31. Delphinium, 40. Fraxinus, 91. Horse-chestnut, 75. Dentaria, 61. Desmanthus, 70. Fumariaceae, 46. Fumitory family, 46. Horse-gentian, 113. Horse nettle, 102. Dewberry, 59. Hound's tongue, 96, 97. Dianthera, 109. Galanthus, 25. Houstonia, 110, 111. Dicentra, 46. Galium, 111, 112. Huckleberry, 87. Dicotyledones, 27. Gama grass, 16. Hydrophyllaceae, 95. Diospyros, 90. Garlic, 20. Hydrophyllum, 95, 96. Dock, 35. Gaylussacia, 87. Hypoxis, 24. Dodecatheon, 90. Geraniaceae, 70. Dog-fennel, 119. Geranium, 70. Indian bean, 108. Dogtooth violet, 22. Geranium family, 70. Indian paint-brush, 105. Dogwood, 86. Geum, 61, 62. Indian turnip, 18. Dogwood family, 86. Gill-over-the-ground, 100. Innocence, 110, 111. Draba, 53. Gleditschia, 69. Ipomoea, 93. Dragon arum, 18. Goat's beard, 58. Iridaceae, 25. Dry strawberry, 61. Golden ragwort, 120. Iris, 25. Index to Flora. 125 Ironwood, 31. Menispermaceae, 44. Parsley, 84. Isopyrum, 39. Menispermuin, 44. Parsley family, 82. Milfoil, 119. Parsnip, 83. Judas tree, 68. Milk vetch, 68. Partridge berry, 111. Juglandaceae, 27. Milkweed, 92. Pastinaca, 83. Juglans, 27. Milkweed family, 91. Peach, 57, 58. Juneberry, 63, 64. Mint family, 99. Pear, 63. Juniper, 14. Mitchella, 111. Pecan nut, 28. Juniperus, 14. Mock orange, 54, 55. Pedicularis, 105. Monocotyledones, 15. Pentstemon, 103. Kentucky blue grass, 16. Moon seed, 44. Peppergrass, 48, 49. Kentucky coffee tree, 69. Morning glory, 93. Pepperwort, 48, 51. Key to families, 7-11. Morning glory family, 92. Persimmon, 90. Kinnikinnik, 86. Morus, 34. Peucedanum, 84. Moss pink, 95. Philadelphus, 54, 55. Labiate, 99. Mouse-ear cress, 49. Phlox, 94. Lady's slipper, 26, 27. Mouse-ear everlasting, 118. Phlox family, 94. Lamb-lettuce, 115. Mousetail, 41. Physoearpus, 58. Lamium, 100, 101. Mulberry, 34. Pignut, 28. Larch, 14. Mustard family, 47. Pimpernel, 89. Larix, 13, 14. Myosurus, 41. Pine family, 12. Larkspur, 40. Pine, white, yellow, spruce, Lauraceae, 44. Nanny-berry, 113. pitch, 13. Leavenworthia, 51. Narcissus, 24. Pink, 37, 95. Leguminosae, 65. Nasturtium, 50. Pink family, 37. Lentibulariacese, 105. Neckweed, 104. Pinus, 13. Lepidium, 48. Nepeta, 100. Plantaginaceae, 109. Lesquerella, 52. New Jersey tea, 76. Plantago, 109, 110. Lilac, 91. Nightshade, 102. Plantain, 109, 110. Liliaceae, 19. Nightshade family, 101. Plantain family, 109. Lilium, 23. Nine-bark, 58. Plantain-leaf everlasting, 118. Lily, 23. Nothoscordum, 21. Pleurisy root, 92. Lily family, 19. Nyctaginaceae, 36. Plum, 57. Linden, 78. Poa, 16. Linden family, 78. Oak, 32, 33; diagram of flow- Podophyllum, 43. Lithospermum, 97. ers of, 32. Poison ivy, 73. Liverleaf, 41. Oak family, 30. Poison oak, 73. Locust, 67. (Enothera, 82. Polemoniaceae, 94. Lonicera, 114. Oleaceae, 90. Polygonaceae, 35. Lousewort, 105. Olive family, 90. Polygonatum, 23, 24. Lycium, 102. Onagraceae, 81. Pomme blanche, 66. Onion, 20. Poplar, 29. Madder family, 110. Onosmodium, 97. Poppy family, 45. Mallow, 78. Orchidacese,'26. Poppy mallow, 79. Mallow family, 78. Orchis, 27. Populus, 29. Malva, 78. Orchis family, 26. Portulacaceae, 36. Malvaceae, 78. Orobanchaceae, 106. Potentilla, 60. Mandrake, 43. Osmorrhiza, 85. Prairie apple, 67. Man-of-the-earth, 93. Ostrya, 31. Prairie turnip, 67. Maple, 74. Oxalis, 71. Prickly ash, 71. Marsh cress, 50. Ox-eye daisy, 119. Prickly poppy, 45. Matrimony vine, 102. Oxybaphus, 36. Primrose, 88. Mayapple, 43. Primula, 88. Mayflower, 87. Painted cup, 104, 105. Primulaceae, 88. Mayweed, 119. . Pansy, 81. Psoralea, 66. Meadow-grass, 16. Papaveraceae, 45. Pteridophyta, 6. Meadowsweet, 58. Papaw, 38. Puccoon, 97. 126 Introduction to Botany. Pulse family, 65. Service berry, 63, 64. Taraxacum, 120. Pyrrhopappus, 121. Sesame grass, 16. Tare, 68. Pyrus, 63. Shad bush, 63, 64. Tendriled trumpet creeper, Sheep-berry, 113. 107. Queen of the prairie, 58. Shepherd's purse, 52. Texas thistle, 102. Quercus, 32, 33. Shooting star, 90. Thallophyta, 5. Silene, 37. Three-thorned acacia, 69. Kanunculaceae, 38. Silkweed, 92. Thuya, 14. Ranunculus, 41. Sisymbrium, 49. Tilia, 78. Raspberry, 59. Sisyrinchium, 26. Tiliaceae, 78. Redbud, 68. Skullcap, 99, 100. Toothache tree, 71. Redroot, 76. Skunk bush, 73. Tooth wort, 51. Rhamnaceae, 75. Sloe, 113. Tradescantia, 19. Rhamnus, 75, 76. Smilacina, 23. Trailing arbutus, 87. Rhus, 73. Smilax, 20. Trefoil, 66. Ribes, 55. Snakeroot, 84. Trifolium, 66. Robinia, 67. Soapberry family, 74. Trillium, 22. Robin's plantain, 118. Solanacese, 101. Triosteum, 113. Rock cress, 53. Solanum, 102. Tripsacum, 16, 18. Rosa, 62. Sonchus, 121. Troximon, 120. Rosaceae, 56; diagrams of Sorrel, 35. Trumpet creeper family, 107. flowers of, 56. Sow thistle, 121. Tulip, 21. Rose, 62. Spear grass, 16. Tulipa, 21. Rubiacese, 110. Specularia, 116. Twin-berry, 111. Rubus, 59. Speedwell, 104. Typha, 15. Rue family, 71. Spermatophyta, 6, 12. Typhaceae, 15. Ruellia, 108, 109. Spiderwort, 19. Rumex, 35. Spiderwort family, 19. Ulmus, 33. Ruta-baga, 49. Spiraea, 58. Umbellifera?, 82. Eutaceae, 71. Spreading yellow cress, 50. Umbrella-wort, 36. Spring beauty, 36. ITrticaceae, 33. Sage, 101. Spurge, 72, 73. Utricularia, 106. Salicaceae, 29. Spurge family, 72. Salix, 29, 30. Squaw root, 107. Vaccinium, 87, 88. Salvia, 101. Squaw weed, 120. Valeriana, 114. Sambucus, 112. Stag-bush, 113. Valerianacea?, 114. Sandalwood family, 34. Staphylea, 74. Valerianella, 115. Sand-bur, 102. Starfoil, 89. Valerian family, 114. Sanguinaria, 45, 46. Star grass, 24. Venus's looking-glass, 116. Sanicle, 84. Star wort, 88. Verbena, 98, 99. Sanicula, 84. Strawberry, 60. Verbenaceae, 98. Santalaceae, 34. Stellaria, 38. Veronica, 104. Sapindaceae, 74. Stylophorum, 46. Vervain, 99. Sassafras, 45. Sumac, 73. Vervain family, 98. Savin, 14. Sumac family, 73. Vetch, 68. Saxafraga, 54. Swedish turnip, 49. Viburnum, 112, 113. Saxafragaceae, 54. Sweet alyssum, 54. Vicia, 68. Saxafrage, 54. Sweet cicely, 85. Viola, 79, 80, 81. Saxafrage family, 54. Sweet viburnum, 113. Violaceae, 79. Schrankia, 69. Sweet William, 94. Violet, 79, 80, 81. Scirpus, 17. Synopsis of main groups of Violet family, 79. Scrophulariaceae, 103. vegetable kingdom, 5. Virginia creeper, 77. Scutellaria, 99. Syringa, 54, 55, 91. Vitaceas, 76. Sedge family, 18. Vitis, 77. Selenia, 51. Tamarack, 14. Senecio, 119. Tangleberry, 87. Wake-robin, 22. Sensitive brier, 69. Tansy mustard, 49. Waldsteinia, 61. Index to Flora. 127 Walnut, 27, 28. Walnut family, 2T. Water birch, 31. Water cress, 50. Waterleaf, 95, 96. Waterleaf family, 95. Water milfoil, 106. Water willow, 109. White daisy, 119. White thorn, 64. Whitlow grass, 53. Whortleberry, 87. Wild hyacinth, 21. Wild indigo, 65. Wild liquorice, 112. Wild potato vine, 93. Wild spikenard, 23. Willow, 29, 30. Willow family, 29. Windflower, 40, 41. Wood betony, 105. Woodbine, 114. Wood sorrel, 71. Xanthoxylum, 71. Yarrow, 119. Yellow poppy, 46. ~~ THIS BOOK IS DUE ON THE STAMPED BELOW AN INITIAL FINE OF 25 CENTS WILL BE ASSESSED FOR FAILURE TO RETURN THIS BOOK ON THE DATE DUE. THE PENALTY WILL INCREASE TO SO CENTS ON THE FOURTH DAY AND TO $1.OO ON THE SEVENTH DAY OVERDUE. OCT 28 1932 SEP 99 1933 JUN 2 1034 LD 21-50m-8,-32 &