|- |- |- |（ （） │ │ │ ） | ， ）. ， |× |- ſ. |- ） ſ. |× | -ſae ſ. |- |- |--ſ.|- | ſ.|- ſae ſ. ae ſ. 00002 (） This Folder belongs in Transfer Case No. The preceding Folder is in - Transfer case No. THE RECORD OF TRANSFERS May be kept on the usual card or the form below, or both may be used. BEGAN USING - º TRANSFER RECORD MONTH DAY YEAR NUMBER | º MADE BY 5. 91.cbcºwºrwicke Co. CINCINNATI, U. S. A. BRANCH STORE's NEW YORK. BOSTON. CHHCAGO. LONDON. No. 66 | Vertical File Foiders furnished in - packages of 100; all right hand tabs. - - º - - - º - -- - º - - º - - - - * - - - - - - - - -- -- - - ~ - - - - - - - º - º - - * - - - - - - º - º - - - - - - - - * *-tt-4 *—r - Fºx --, * v-- ~~~~ * > w- out-º-c- *-*. -6-4- *~}º- § tº. . ſº- (~~~~ *-*.*, *-*****) - sº, i-º-, . 3.W., Sele IIT, º The Relation of Winter in the xerofy ty of Certain Evergreen Peat Bog Ericads . A Dissertation Submitted to the Faculty of the Department of Literatur, Science, and Arts of the University of Michigan in Candidacy for the Degree of Doctor of Philosophy, August 1912. loy Frank Caleb Gates, A. B. O U T L I N E . page • Introduction — — — — — — — — — — — — — — — — — — — — — 1. The problem. Acknowledgements. General Discussion - - - - - - - - - - - - - - - - - - i – 5 Existence of organisms. Fundamental requirements of life. Absorption. Assimilation. Respiration. - Excretion. Reproduction. Habitat. Pisiological Water supply. Xerofytic adaptations. Meaning. Some reservations. The deciduous habit as a xeroflytic adaptation. Evergreen character of the bog ericads. * {e ericads xerofytic because of winter or summer conditions? Xerofytic adaptations to conserv water because of the difficulty of absorption because of: Poorly developt root system, Low oxygen content of the water, Low aeration, Root excretions, Bog toxins, Mycorhizal fungi, Low temperatur of the bog water, Biological processes rather than chemical natur of soil, Acidity of the soil. Bog and swamp plants. Significance of fysical and fisiological water supply. The bog habitat as detrimental to plant growth. The study of the stem in its relation to the problem. The study of the leaf in its relation to the problem. Classification of xerofytic response. Retarding transpiration in the leavs. Checking transportation in the conducting tissue. The accumulation of water. The position of bog ericads in this classification. Description of the peat bog habitat - - - - - - - - - - - 6– 7 Definition of peat bogs. Distribution of peat bogs. Consideration of particular peat bogs. First Sister Lake, Ann Arbor, Michigan. Description of the plantº associations and their - Successions. Carex filiformis association. ------ Chamaedaphne association. Iris association. Aronia-Vaccinium association. Salix-Gephalanthus association. Larix association. Mud Lake, Washtenaw County, Michigan. Aronia-Vaccinium association. Larix association. -- Picea association. Seasonal history of peat bog plants — — — — — — — — — 8-12. Ericads. Chamaedaphne calyculata- Winter. Detaild description of the plant in the Chamaedaphne association. Its behavior in other associations. Spring. Greening out of leavs. Bending of leavs into summer position. Blooming. Summer. Development of the shoots of the year. Large leavs. Small leavs and flower buds. Approach of Winter. Details of the changes from summer to winter characteris- tics and position. Variation in different associations. Andromeda glaucophylla. Vaccinium macrocarpum. Deciduous trees and shrubs. Species represented. Winter condition. Growing season condition. Herbaceous plants. Seed reproduction. Vegetativ reproduction. Summer conditions. Structur of certain peat bog plants - - - - - - - - - Root system. - - - - - - - - Depth. Mycorhiza. Resin. Root, hairs. Relation to aeration. Water supply. Summer. Times of drought. Winter. - - -- - - - -- - - - - Times of very low temperatur. Conducting system — — — — — — — — — — — — — — — — — — General description. Ericads. Deciduous shrubs. Herbaceous types. Conduction of water. References to literatur. Control by transpiration. Relation of oonduction to transpiration. Utilization system - - - - - - - - - - - - - - - - - - 17. Leavs. Structur of ericad leavs. Xeroflytic adaptations. Cutin. Position of the stomates. - - --- º - - Palisade. Wax. Bloom. Hair. Scales. Leavs revolut. Mechanical tissue. Transpiration of water. Variations in ability to liv in bog soil. Evergreen habit. Winter and summer positions of leavs. Strutuwys of Chamaedaphne leavs developing out of their natural conditions. Function of water loss. Fotosynthesis. Cooling effect of vaporization of water. Removal of the products of respiration. Transportation of mineral matter from the soil. Relation of water loss to the evaporating power of the air. Relation of soil to water loss. Summer. Winter. Relation of the maximum transpiration to the maximum evaporating power of the air, in southern Michigan. In cuttings. In potted plants. Incipient drying. Stomates as regulators of transpiration. Literatur. Present investigation. On cuttings. On potted plants. On plants in the field. Experimentation - - - - - - - - - - - - - - - - - - - - 23-81. Materials and methods - - - - - - - - - - - - - - - - 23–26. Experimental method. Preparation of material. Collection. Set up. - Determination of transpiration, methods In cuttings. In potted plants, Chamaedaphne galygulata from the Ghamaedaphne association, the basis of comparisons. Detai-mination of leaf %rea. Method of calculating data to standard basis. Methods of plotting and interpretation of results. Criterion of experimentation. Determination of the volumes of the leavs. Correlation of the volume with leaf surface. Determination of area of conducting system. Determination of the rate of conduction. Experiments upon transpiration during the Winter - - - 26-42. General discussion. Comparison of Herbaceous plants, Deciduous shrubs and trees, and Evergreen shrubs and trees. Purpose and material. Experiments of Jan. 7–13, 1912 on potted ericads outdoors. Experiments of Jan. 13–17, 1912 on potted ericads outdoors. Experiments of Feb. 27–29, 1912 on a cutting of Chamaedaphne Outdoors. Experiments of Mar. 1-2, 1912 on cuttings outdoors - Experiments of Feb. 5-5, 1912 on a potted spruce outdoors. Experiments of Feb. 10-12, 1911 on cuttings outdooors. Experiments of March 5–8, 1912 on cuttings outdoors. Consideration of experimental data of outdoor work - - - - 31. Relation of exposur to the transpiration ability of the ericads. Relation of transpiration to Temperatur. Relativ humidity. Daylight and darkness. Absolute values of transpiration under Winter conditions. Deciduous vs evergreen habit. Absorption of Water vapor from the air. Rateeof transpiration as a fytogeografic factor. Experiments in transpiration under laboratory conditions. Experiments of Dec. 2-12, 1911 on cuttings in the greenhouse. Experiments showing influence of solution temperatur upon transpiration. — — — — — — — — — — — — 54. Experiments of Feb. 27–28, 1912 on cuttings in the laboratory. Experiments of Mar. 1, 1912 on cuttings in the laboratory . Experiments of Mar. 3-6, 1912 on cuttings of Chamaedaphne in the laboratory. Experiments of Mar. 5-6, 1912 on cuttings in the laboratory. - h - Survey of experiments of Feb. 27 to Mar. 6, 1912 — — — 36 . Relation of the temperatur of the air and of the solution to transpiration. Relation of sunlight and darkness to transpiration. Relation of a cold source of water supply to transpiration. Summary of the relation of the pelatier-ef soil temperatur to transpiration. - - - - - - - - - - - - 58. Discussion. General summary of transpiration in winter - - - - - - - - 41. Experiments upon the rate of Conduction during the winter 42–51. Experiments of Feb. 22–23, 1912 **oratory. Experiments of Feb. 24, 1912 in the attic. Experiments of March 3, 1912 on deciduous and evergreen shrubs in the laboratory. Experiments of March 5, 1912 under different laboratory conditions. Experiments of March 10, 1912 in the laboratory. Experiments of March 12, 1912 in the laboratory. Summary of the experiments showing the relation of solution temperatur to the conduction of water. - - - - - 46. Experiments showing the conduction of different evergreen ericads and its relation to transpiration- - - - - 47. Experiments upon the relation of rate of conduction and transpiration in Chamaedaphne under different laboratory conditions. - - - - - - - - - - - - - 48. Conclusions. - - - - - - - - - - - - - - - - - - - - - - - 51. The relation of winter in the xerofytism of peat bog ericads 51-52. = 1 - Experiments upon transpiration during the summer - - - - 55-70. Purpose, materials and method. Experiments of May 6–7, 1911 on cuttings outdoors. - - - 54. Experiments of May 22–23. 1911 on cuttings outdoors. - - - 55. Experiments of June 14-15, 1911 on cuttings outdoors -- - 55. Experiments of June 15–16, 1911 on cuttings outdoors - - 56. Experiments of June 16–17, 1911 on cuttings outdoors - - 57. Experiments of May 6–7, 1912 on cuttings in the laboratory 59. Experiments of June 4–6, 1912 on cuttings in laboratory - 60. Experiments of June 18–19, 1912 on cuttings in laboratory 60. Experiments of June 24–25, 1912 on cuttings in laboratory 61. cuttings and Experiments of June 50-July 1, 1912 on Apotted plants 62. Experiments of July 1–5, 1912 on cuttings and potted plants outdoors - - - - - - 64,65 Experiments of July 4–6, 1912 on cuttings and potted plants outdoors — — — — — — 64,ée Experiments of July 8–9, 1912 Orl cuttings in the cupelo – 68. Discussion of the experiments of June 30–July 1, 1912 on cuttings and potted plants ---------------------- €7. Experiments upon rate of conduction during the summer----- 70-72. Method. Experiments of July 6, 8 and 9, 1912. Conclusions. General conclusions of the summer experimentation on transpiration and conduction - - - - - - - - - - - 72–73. A knowledge of the facts. A differentiation of the facts. The relation between transpiration and conduction and xeromorfy. The absorption of water vapor from a saturated atmosfere — – 74-78. General. Experiments of June 29-30, 1912 on Chamaedaphne. Experiments of June 30, 1912 on Chamaedaphne. Experiments of July 4, 1912 on Chamaedaphne. Experiments of June 30-July 1, 1912 on Andromeda and Vaccinium. Experiments of July 2–3, 1912 on Andromeda. Bºxperiments of July 8–9, 1912 on Picea mariana and Larix. Conclusions. Conditions in natur. Experimentation upon stomates - - - - - - - - - - - - - - -- 78-81. General. Methods and materials. Results. "Normal" rate. Experimentation during the daytime. Closing of the stomates. Behavior of the stomates on plants which hav been collected. Behavior of the stomates of wilted plants. Behavior of the stomates of dry plants. Behavior of the stomates of aéral leavs kept under water. General discussion of the rehation of stomates to transpiration. General discussion and conclusions. - - - - - - - - - - - 82-86. Role of water in plant life. Determination of water loss (transpiration) as a means of experimentation. Expression of results. Material of experimentation. Relation of cuttings to potted plants. Behavior of the stomates of peat bog plants. In natur. In cuttings. Water loss (Transpiration) Relation of the deciduous to the evergreen habit under Winter and summer conditions. Relation to the evaporating power of the air. Absolut Values of transpiration in Ghamaedaphne. Maximum value obtaind in hydrofly tic plants. Relation of winter in transpiration and conduction, and its effects on structur. Effect of xeromorfy on summer transpiration. Relation of snow to killing at low temperaturs. Conclusions. Summary - - - - - - - - - - - - - - - - - - - - - - - - - - 87. Bibliografy of the works cited- - - - - - - - - - - - - - - 91-97. Illustrations - - - - - - - - - - - - - - - - - - - - Plates 1 to 19. * - 3: INTRODUCTION . Of late years considerable attention has been drawn toward the apparently anomalous condition of several plants With obvious xerofly tic modifications, yet living in bogs With an apparently un- limited Water supply. Many explanations of this apparent anomaly hav been attempted. It was with a desire to attain further know- ledge upon the question that the author entered upon this piece of research work in the Botanical Department of the University of Michigan in the fall of 1910. The work was carried on under the direction and supervision of Professor F. C. Newcombe. To him I am greatly indested both for the opportunity to work and for his stimulating criticism thruout the work. To Dr. H. A. Gleason and to Dr. J. B. Polleck, both of the University of Michigan, I am also indebted for helpful conferences during the course of the work. To Mr. W. B. McDougall, of the Uni- versity of Michigan, I am further indetted for the examination of material for the presence or mycorhiza. Simplified spelling is used thruout the work. The nomenclatur is that of the 7th edition of Gray's Manual. GENERAL DISCUSSION . ſ In order to maintain existence it is necessary for an organism to fulfil the fundamental requirements of life: it must be able to take in food (absorption), it must be able to digest its food (assim- ilation), it must be able to oxydize or otherwise rearrange its Substance to obtain energy (respiration), it must be able to elimi- nate its waste products (excretion), and it must be able to perpetu- - 2 - ate its kind (reproduction). Further it must be able to perform all these functions in situ in its particular individual environ- ment. As these individual plants can not migrate they must be able to accoºdate themselvs to the changing environmental conditions or die. That they flurish from year to year in healthy condition is unquestionable evidence that they are able to cope with their envir– onment. Their ability to invade genetically lower associations of plants indicates that they are thriving rather than just merely existing in their habitat. Altho a living plant is always the expression of the integration of environmental and hereditary factors, the most important single º factor in the environment is the fisiological water supply. The º º modifications of plant structur which lead to the conservation of the water supply are termd xeroflytic adaptations or xerofly tig reactions. The presence of Xerofytic adaptations does not necessarily º predicate that the amount of Water used by the plant is relativly small, but that the ratio of the amount used to that which the plant obtains tends to become less than unity. Some so-called xeroflytic plants use as much or more than ordinary mesofytic plants, as Groom (1910) found was the case with Larix decidua. They are xerofytic, however, because they can not absorb a large amount of water in proportion to that which theºsºire. This is particularly true of the summer when plants hav their transpiring organs. The loss of leavs during the winter is quite rightly regarded as a xerofytic adaptation. The bog ericads which were investigated, however, retain their leavs during the winter. This opens at once the question, Are these plants xerofytes because of their summer or their winter environment. As it may be safely rz -- -- assumed that the evergreen habit is an hereditary character in the ericads, the reaction to the environment necessitates the xeromorfy. The question is a rather broad one and several lines of attack suggested themselvs. All, hower, bear more or less directly on the water relation. It would seem at first glance, that plants which grow in bogswhere there is practically always an obvious £ysical water supply would not be restricted in its use, but the various xeroflytic adaptations argue for the conservation of Water in the plant - The ability of the plant to absorb water is limited on account of poorly- developt, shallow root systems, low oxygen content of the Water (Dachnowski, 1908 and Hesselmann, 1911a and 1911b and others), low aeration (Transeau, 1905-6, Dachnowski, 1909, and Free, 1911), root excretions (Livingston, Britton and Reid, 1905, and Schreiner and Reed, l007a and 1907b), bog toxins (Livingston, 1905 and Dachnowski, 1908, 1909 and 1910), the necessary of myczorhizal fungi in some species, the low temperatur of the soil water (Sachs, 1860, Kosaroff, 1897 and especially Transeau, 1905-6) and biological processes rather than chemical differences in the soil (Dachnowski, 1912). Much stress can not be laid upon the acidity of the soil, as Schimper (1898) has done because of latter investigations. The acidity is very low and differs in airreºt, associations, as the following figurs from Transeau (1905-6) show. The figurs presented represent the proportion of a normal acid solution. First Sister Lake, Carex Association: • OOO 66 • OOO 94. Chamaedaphne " • OO 152 • OO 119 Larix º • OO 165 .00179 .00227 ... 00:258 That acidity is a necessary factor in the soil for the growth of trail- ing arbutus (Epigaea repens) and of the blueberry (Vaccinium corymbosum) were most admirably demonstrated by Goville (1910 and 1911), who found - 4 - that poor aeration was usually the real cause of poor growth and not acidity. Acidity may, however, be inimical to certain crops as the investigations under the direction of Prof. H. J. Wheeler, publisht by the Rhode Island Experiment Station, have demonstrated. Sampson and Allen (1909) in experimenting upon the influence of fysical factors on transpiration, found that some of the common acids, as a rule, accelerated and alkalis retarded transpiration and that weak solutions often produced as markt effects as strong ones. - Where bog and swamp plants grow in the same area they are subject- ed to similar conditions. As both thrive on the amount of Water they obtain, one can not predicate that simply a difference in the ability to absorb water made a species a bog or a swamp plant. The fact that certain plants living in apparently obvious abundance of water supply are structurally modified to conserv water led to the differentiation of fysical and fysiological water. Reduced to its simplest terms this means that plants may be subjected in their environment to a water supply of which they can not make full use. The part that the plants cannot obtain is known as the fysical in contradistinction to the fysiological water supply. This redily led to the question as to why the plants can not make full use of the water present. Many answers hav been attempted and it semms quite likely that the true answer is a combination of the different reasons rather than any Single reason. The problem presents an obvious result obtaind from a he Wildering mass of causes, whose interacts are not yet known. It is recognized that there is something detrimental to plant growth in bogs. This is a matter of common information both among Scientists and farmers who try to use the land for their ordinary crops. The work of Livingston and Dachnowski throw the clearest light on this side of the question. The water absorbed is conducted up thru the stems. A study of the - 5 - stem structur would show whether the ericads formd a group by them- selvs or whether there was no essential difference between these bog plants and swamp shrubs. It might be possible to find a numerical relation between the area of conducting tissue and the leaf surface which would be radically different for swamp plants and bog ericads. In either case the ability to conduct water must be adequate as the plants thrive. From the stem the water passes into the leavs where the largest part of it is vaporâzed and passes out of the plant thru the stomates. Xeroflytic response may be classified into means retarding transpiration in the leavs or transpiring organs, checking transport- ation in the conducting tissue and provision for an accumulation of Water. In the peat bog ericads used in the course of this investi- gation xeroflytic response was very evident in the leavs, but was not accompanied by water storage tissue. This made the xeromorfic structur more necessary on account of the poorly developt rootsystem. The evergreen habit, with its relativly large exposur of leaf surface, Calls for greater activity of the root system thruout the winter, for transpiration still continues even when the thermometer is below 0°C. (Hartig, 1860, Burgerstein, 1875 and others), That means to reduce the loss of Water are all the more necessary under winter conditions is obvious. DESCRIPTION OF THE PEAT BOG HABITAT. (cf. Frºh and schrºter, 1904, Davis, 1907 and Harshberger, 1909) A brief description of the natur of the environment and the Char- acteristics of the vegetation of the peat bog may well be given con- sideration, befor dealing with the experimental work. Peat bogs, in general, are of northern distribution (Transeau, 1903 and Harshberger, 1911) and consist in habitats in which the soil is the partially decayed remains of plants with virtually no admixtur of mineral soil. The vegetation very frequently commences at the border of a lake in a depression. It develops out upon the tºº.º. may ultimately obliterate it. The constant dropping of materials from the mat gradually fills up the bottom. The greater part of the observations and material for this in- vestigation was obtaind at First Sister Lake, a little west of Ann Arbor, Michigan. There the plant associations exhibited a very markt zonation as shown in fig 2, Pºle". which has been described by Weld (1904), Transeau (1905-6) and Burns (1906). The normal , successions between these associations are shown in Ptaſe (4.. The most important in the formation of peat are the Carex filiformis and the Chamaedaphne associations, but especially the former (Davis, 1907). It will not be necessary to go into a detaild description of these associations but merely to mention a few pertinent facts. Altho not necessarily the first vegetation to appear, the Carex filiformis association, an association of herbaceous plants, mostly sedges, forms the mat which is the beginning of peat formation. In- Vading upon this mat comes Chamaedaphne and Sphagnum. Thus a growth of small sized shrubs is instituted, which consists largely of the ericads, Chamaedaphne galyculata, Andromeda glaucophylla and Vaccinium Imagrogarpum and Sphagnum, with a few secondary species, such as ry Sarracenia purpurea, Pogonia ophioglossoides, Arethusa bulbosa, etc. Between the Chamaedaphne and Carex filiformis associations there is usually a tension zone — the Iris association of herbaceous plants with Iris versicolor, Aspidium thelypteris, Eupatorium perfoliatum, Potentilla palustris, Menyanthes trifoliata, Sagittaria latifolia and Salix pedigellaris. If sufficient soil is formd, an association of larger shrubs invades the Chamaedaphne association. This is taking place rapidly at First Sister Lake, where it is represented by Pirus (*Aronia) melanocarpa, Nemopanthes mucronata and Gaylussacia baggata, While Vaccinium corymbosum is locally absent. If southern or swamp plants get the ascendency, Salix and Gephalanthus occidentalis, Rosa garolina and Spiraea salicifolia are the most common. On the other hand if bog plants invade the Aronia-vaccinium association, the vegeta- tion is characterized by trees, Larix laricina and Acer rubrum. At Mud Lake, in the northern part of Washtenaw County where supplementary work was carried on, the Aronia–Vaccinium association Was well developt. The Larix association was not so well developt but a more advanced stage was represented by the bog spruce, Picea mariana. - 8 - THE SEASONAL HISTORY OF PEAT BOG PLANTs. Chamaedaphne calyculata- Taken at the beginning of winter Chamaedaphne is an evergreen shrub, having therappearance of a nearly uniform stand at the top but aggregated into clumps at the base. The centers of these clumps are packt, with Sphagnum. The root system is excedingly shallow and nearly always relativly poorly developt. Neither roothairs nor mycorhiza are in evidence. The leavs of Chamaedaphne plants in the Chamaedaphne association are easily divided into two groups, one of which occurs a little wayſ back of the ends of the twigs. The leavs of this group are rather thick, flat and coverd beneath with brownish scales. They are dark green changing to brownish at the beginning of Winter. They are nearly always upright, or nearly so, with their upper surfaces inner- most. The other type or leaf is very small and occurs at the ends of stems. In its axil is a flower bud. This type of leaf is thick, strictly upright, and densely coated with scale beneath. The base of the midrib often remains slightly greenish even thruout the Winter. In Chamaedaphne plants growing in the Carex association, many of - the larger leavs drop off with the approach of winter. There remain medium sized and small leavs which are very silvery beneath. In plants in the Larix association, the numerous large leavs finally turn brown and generally become more or less revolut. There are very few of the small leavs and little flowering: occurs. In severe winters most of the leavs of this plant in this association dry up if exposed. The stems of Ghamaedaphne plants in the Carex association are a trifle Smaller in diameter but much tuffer than those in the Chamaedaphne association, while those in the Larix association are very much more slender. As spring begins to be felt the petiols and midribs become green - 9 – and later this spreds to the laminae of the leavs. The larger leavs begin to bend back. This is most often accomplisht by a simultaneous bending back of the midrib at the tip together with the folding back of the edge of the leaf, but in the end it appears as tho the entire process Were brot about by the simple bending of the leaf or petiol at their junctur. At this time the blossom buds unfold into little White, pendent flowers which open but very little. The leavs in whose axils they are located begin to green out and bend out flat, sometimes enlarging a trifle. The process is very rapid if continued high temperatur prevails at this time, as in 1911. The mass effect becomes green in place of the brown of winter. During spells of protracted drought, as in June 1912, this bending back of the leavs is at a minimum and they remain more nearly upright. Soon after the period of blooming the buds in the axils of the larger leavs back of the inflorescence expand and grow out into the leafy shoots of the year. About this time some of the large leavs begin to fall off one by one. Byſſhe end of summer the entire work of fotosynthesis has been put upon the younger leavs. In a normal year the seeds ripen at the beginning of summer and are shaken out Of their capsuls. During a very severe winter as 1911–12, the upper parts of the plants are killed back to about the line of protection by snow. The presence of the ded leavs and twigs at the top prevents the uniform green appearance which this vegetation normally develops soon after the growing season opens. During summer the normal vegetativ processes go on. At first large leavs are produced but towards the end of the activly growing periodºne branches grow out into slender, nearly horizontal twigs which bear the small leavs in whose axils flower buds are developt. - 10 - The coming of winter is evidenced in the gradual change of color of the leavs from green to dark and duller green and then into brown. Along about time for frost the leavs lose their green color, more usually from the tip down. Green changes from darker to darker green, which by the end of November becomes brown, slightly tinged with red. These color changes take place in all the leavs but are most pronounced in the large size ones. The color changes usually procede from the margin to the midrib. The midrib – except sometimes at the very tip - remains green after the lamina has become brown, but later exhibits color changes. The petiol becomes deep red and this color procedes a little ways up the midrib but givs place to reddish brown. The leavs are tuff, yet very pliable. The small leavs are more or less silvery beneath, due to small roundish scales which quite densely cover the sur- face. In the large leavs the scales are spred out over a larger area and do motº therefor giv a silvery appearance. The small leavs are more nearly isodiametric than the larger ones. The leavs become up- right, at least the petiol and lower portion of the lamina, while the tip may be curled back 59 to 10° or more. Upright branches hav the leavs parallel to them and more or less enclosing them. The lower surfaces are outward. Horizontal or inclined branches hav the leavs folded up irrespectiv of the angle of the branch. These same changes take place in plants in the Carex association, usually earlier in the fall and later in the spring than in the Chamae- daphne association. The large leavs are more liable to be cast off 'befor the end of winter. In the Larix association, however, the plants tend to exhibit these same changes but the degree is nowhere so pro- nounced and the leavs are more likely to dry up and die during the Winter. - ll - Andromeda glaucophylla- In a general way the seasonal history of Andromeda is much the same as that of Chamaedaphne. During the early part of the growing period large leavs are produced and later smaller leavs and the fºllow- er buds for the coming year. The leavs are upright at first but later bend down so as to be nearly perpendicular to maximum sunlight. Thus - they remain until the close of the growing season when they again become upright and in that position pass the Winter. They become brown during the winter and the leaf margins then are more strongly revölut. With the coming of spring they green out and bend down and remain until the new crop of leavs is produced. A few leavs occasional- ly remain into the second winter. As a general rule, plants of Androme- da are protected by a complete covering of snow during the winter. vaccinium macrossroºm. The vegetational cycle of this plant is quite similar to that of both Chamaedaphne and Andromeda. The new leavs, developt in spring, are upright, reddish green above and white beneath. They gradually bend in a position nearly perpendicular to maximum sunlight and remain so until the approach of winter. Then the leavs bend upwards – on horizon— tal stems so that they stand back to back above the stem, and on vert– ical stems, back to back along the stem. The color of the upper sur- face becomes darker and darker green and givs place to a deep, dull red, which increases during the course of the winter. The petiols and mid- ribs are bright red. With the opening of the season the leavs become horizontal by curling back from the top, followa by epinastic growth at the junctur of petiol and blade. Leavs may frequently remain in use for two years and sometimes longer. As these plants grow close to the ground they are protected by a covering of snow in the winter. -12– Deciduous Trees and Shrubs. The seasonal histories of the trees and of the majority of the shrubs of the region are so similar that they may all be groupt under one. The principal trees are Larix laricina and Acer rubrum, and the pricipal shrubs are Pirus (=Aronia) melanocarpa, Salix pedicellaris, Salix discolor, Salix sericea, Spiraea salicifolia, Betula pumila, Nemopanthes mucronata, Ilex verticillata, * Gaylussacia baccata, Gephalanthus oggidentalis, Sambucus canadensis and Rosa carolina • During the winter these plants are leafless which greatly reduces the transpiration. The snow that usually is present during the Winter protects the root system and lower part of the stem from danger of excessiv low temperatur during the winter but the upper parts of the trees and bushes are not so protected. They must be able to resist Water loss thru their own modification. This is sufficient for the Severest, Winters in Southern Michigan, as that of 1911–12 demonstrated. During that winter Spiraea was the only leafless shrub to be killed down to the snow line. With the opening of spring the buds swell and develop into bran- ches bearing leavs which carry on the work of the season. A separation layer is formd at the approach of winter at the base of the petiol and by the time winter has set in the leavs hav fallen. Herbaceous Plants. The seasonal history of the herbaceous plants follows two general lines. The plant which has developt during the growing season may die down completely befor winter, leaving seeds to reproduce it the fol- - - - - Vegetativly lowing year, or it may die down to the ground and be Areproduced the following year from underground stems, bulbs, rootstocks or buds. Either of these ways is an absolute Xeroflytic adaptation on account of Winter conditions, but does not interferer with summer development. - 13 - Consideration of the Structur of Gertain Peat Bog Plants • (Cf. Solereder, 1899) During the course of work a number of sections of different parts of the plants was made to become acquainted with the anatomy of the plants concernd. Root System- Without exception all of the forms dealt with had a very shallow root system which was usually very poorly developt in comparison with the root systems of ordinary plants in ordinary soil. It was in direct contrast to that of the xerofytes of the desert (Cannon, 1911) Two general types of roots could be separated according to the presence of absence of mycorhizal fungi. Most of the ericads hav mycorhiza but in so far as the author was able to discover, mycorhiza was not found upon the roots of Andromedia nor Chamaedaphne. These results are substanciated by Transeau (1905-6) and by McDougall, who is now carrying on researeh work upon mycorhiza. In Working over the material furnisht him by the author, McDougall found that Androme- da occasionally gav evidences of mycorhizal appearance the further investigation faild to reveal their presence. My corhiza was found on Larix laricina, Acer rubrum and Vaccinium macrocarpum, but was not noticed on any of the following plants: Carex filiformis, Sagittaria latifolia, Eupatorium necroliata , Dulichium arundinaceum, Asclepias incarnata and Aspidium thelypteris. The absence of mycorhiza on Chamaedaphne and these other plants demonstrates that mycorhiza are aot a necessary adaptation to the bog environment. The presence of resin deposits (Transeau, 1905-6) isoften a notable featur of the roots of bog plants. Root hairs were not, observd, altho Transeau (1905-6) found that in cultur solutions Which were well aerated normal roots with root hairs were produced in Larix. - iº - During the summer the roots of the bog plants, at least apparently, hav an abundant, water supply, altho as a matter of fact the Sphagnum which surrounds the roots may be ſysiologically dry even when apparent- ly wet, due to the great ability to soak up and store Water (Frºh und Schrºter, 1904 and Davis, 1907). In general, however, there is standing water beyond the ability of the Sphagnum to absorb and there- for the bog plants hav a supply to draw on thruout a normal season. seasons of drought would accordingly be the critical ones and the season of 1911 was a case in hand. In so far as could be observd it did not appear that Chamaedaphne, Andromed a glaucophylla or Vacci- nium macrocarpum were suffering from lack of Water even on the hottest and driest days. The leathery natur of their leavs makes it nearly impossible to tell whether the plants are wilting or not. When herbace- ous vegetation was obviously wilted the leavs of the ericads did not appear other than normal. In the natural distribution of these plants droughts are not sufficiently extreme nor of long enuſ duration to dry up the Sphagnum except oceasionally at the very uppermost layer. The great ability of Sphagnum to soak up and retain water localizes the Water within reach at the expense of surrounding area. This often results in the elevation of the watertable under the bog several inches above that of the surrounding country. This condition obtains only during summer and fall. With the approach of fall the bending up of the leavs reduces the demand upon the roots for absorption. Taking into consideration the rarity of real drought conditions of long duration, it is evident that the root system in the bog habi— tat is able tº more than merely maintain these plants within their normal range thruout drought conditions. The xerofytic adaptations of the transpiring organs, of course, materially aid by lessening the demand upon root absorption. - wºw tº - 15 - During the ground is normally more or less frozen. On account of the low position of bogs and the rapid evaporation, it is more subject to early and late freezes than the surrounding country. Altho the ground may be frozen, the covering of snow prevents the access of very low temperaturs to the roots. In spite of the fact that the ground is frozen, it is evident from the continual water loss of the above-ground parts that some water is being absorbed by the roots, quite likely the water vapor evaporated from the ice into the spaces which become opend around the roots soon after the freezing of the ground. Absorption of water by roots has been demonstrated for temperaturs below freezing by Kosaroff (1897). (down to -100C) At any of the temperaturs prevailing Awhen roots were dug up, it did not appear that any part of the plant was frozen. All Peº pliable to handling. The exposur of severd parts of gunadº /* to -259C resulted in freezing and loss of pliabilty so that they crackt when bent. It was noticed repeatedly that the leavs which had been exposed to the severest weather of the winter, including a temperatur of -89°C, were dry and crackt like dry leavs jº. Later it became evident, that these leavs had been killed. Beyond this simple test, whose limits of accuracy are not known, there were no suitable means of determining in situ in the field whether plant tissue was frozen. Conducting system. Water absorbed by the roots must be gotten to the leavs where it is utilized. This is the raison d'être for the conducting system. As shown in the drawings the conducting system of the bog ericads is a relativly narrow ring of thick-walled xylem cells with small lumina just outside of the wood. There is a very striking similarity in the appearance of the cross section of the true ericads, ghamaedaphne and Andromeda which is very closely approacht by Vaccinium, lately included in the Ericaceae. The type of stem represented in bog ericads is strikingly different from that of other bog shrubs in the relativly smaller amount of conducting tissue and the smaller lumina of its cells. It always appears definitely as a ring around the wood rather than in separate bundles - The stems of the bog herbs are all quite different from those of the bog ericads. Among the herbs different types of structur are exempli- fied by Sagittaria, Aspidium, Asclepias, Eupatorium and others. Among the bog shrubs the ericad type stands out distinctly from all the other shrubs – there being far less difference between the structur of any two ericads than between an ericad and any other shrub. Just how the water is conducted from the roots to the transpir– ing organs is not a closed question. For a discussion of this question the reader is refered to the literatur, particularly Copeland (1902), Dixon (1909), Overton (1911), Renner (1911), Schermbeek (1911) and Babcock (1912). The results of this investigation show that the fundamental control of rate of conduction is exerciad by the rate of transpiration. Just as the rates of absorption and of trépiration do not exactly accord (Burgerstein, 1904 and many others), neither do the rates of conduction and transpiration. Increase of transpiration, however, always means increase of conduction, and a decrease in tran- spiration a decrease in conduction, tho not always in the same pro- portion. This is in accordance with the cohesion theory of Dixon (1909) further elaborated by Livingston. When a plant is not fully turgid, an immediate any check to the rate of transpiration does not find a proportionate check in the rate of conduction or absorption, but these latter con- tinue until turgidity is restored. Consequently measurements of – 17 — absorption or conduction can not be considerd as being interchangeable with those of transpiration until the plant is fully turgid - Utilization System- The place where the great bulk of the water absorbed is utilized is in the leavs, or transpiring organs. Altho the external appearance of the leavs of various peat bog plants may be very different, the general internal structur is more nearly similar and twº of the various ericads is quite similar to each other. Several well--sº xerofytic & adaptations are present, notably the strongly cuticularized epidermis, absence of stomates on the upper surface, a well-developt palisade layer 1–3 cells thick, stomates frequently sunken and coatings of wax, bloom, hairs, or scales. Mechanical tissue is present and accounts for the suppression of the ordinary symptoms of wilting. Usually the leavs are at least slightly revölut - those of Andromeda and Salix candida strongly so. The leavs are usually dark green in color, often reddish at the beginning and close of the vegetativ season. The abundant presence of cutin in the evergreen ericads as an efficient xerofytic adaptation against loss of water at all times, but especially in winter, has been brot out by Wiegand (1910). A considerable amount of water is transpired by many bog plants and the loss may be as great or greater than that from mesofytic plants of the same vicinity. This suggests that it is the maximum rate to which the plant may be subjected rather than the amount of Water lost is the important consideration. If the amount of food material is correlated with the amount of water lost, there must be considerable more water absorbed in the bog habitat which is notably deficient in available food material (Kedzie, 1893, Hopkins, 1904, Transeau, 1905-6). Plants that normally grow in non-bog conditions, e.g., white pine and spruce, when growing under bog conditions are much dwarft and stunted, and their leavs exhibit very pronounced xerofytic modifications, so much - 18 - so as to hav receivil specific designation. Some plants, as Populus tremuloides, and Poa pratensis, that may - grow either in bog or mesofytic soil do better in the latter situat— ion and always exhibit a pronounced xeromorfism in the ++-ºre bog soil. Some plants demand bog conditions and even then hav xerofytic modifica- tions, as Coville (1910) demonstrated in the case of the blueberry. During the growing season all of the bog plants hav their activ, transpiring organs but the great majority do not retain them during the Winter. In every case where leavs are retaind their winter posi- tion is different from their summer one. This position is usually an upright one. In the case of evergreen conifers the leavs are more closely apprest to the twig. The young leaf as it comes out, in the spring is also upright) at least as long as it is tender. What at first seems peculiar is that the lower, stomate-bearing surface is directed outwards, the more exposed position. A moment's consideration, how- * . lººsa. - ** º ºr - ºttestiºnſ. The Stomates of the lowſer side are ever, easily solves the well protected by wax, hairs, or scales, and are light in color, while the dark upper surfaces absorb a much greater amount of radiant energy, which would raise the temperatur of the mesofyl cells and lead to greater loss of water. The upright todºo top position of the leavs during winter is really a xeroflytic modification reducing the amount of radiant energy absorbed at a time when it would be needlessly disſippated in increase of water loss which the absence of fotosynthesis does not occasion. Starch tests made on different days during the Winter in the morning and in the evening on both cloudy and Sunny days usually dis- closed a little starch in the lower part of the red petiols but no traces were detected in the lamina. Accordingly it is safe to assume that no extra radiant energy is needed for food manufactur and the leavs react, assuming a position which givs them a minimum of radiant energy . - 19 - An examination of some sections of Chamaedaphne leavs which had developt upon twigs collected in December and left standing in water in the laboratory window disclosed weakly developt palāsade tissue. As the development of palisade is one of the commonest indications of xerofytic tendency, this indicates that the uniform development of palisade in Chamaedaphne plants in the Carex and chamaedaphne associ- ations is a response to the environmental conditions. Leavs produced on these plants growing in the Larix association hav poorly developt palasade. Such leavs are easily killed in even average winters and Ghamaedaphne does not long persist in typical Larix associations. The leafy shoots that developt on cut stems kept in water in the laboratory and in the greenhouse lived for but two or three weeks, even tho roots were developing. This took place in bog water, snow water, tap water and distilled water alike. As a result of this in- ability to become adjusted to a water cultur no experiaents could be performd on such material. The loss of water by the leavs exercises a twofold function. The excess of radiant energy absorbed and not used in fotosynthesis could easily raise the temperatur of the leaf to the death point during hot Waves, were it not distrated in vaporizing water. Darwin, (1904) thru the use of a resistance thermometer and Gallendar recorder, demonstra- ted that, with the check to transpiration which comes with induced closur of the stomates, the temperatur of the leaf rises. Normally this higher temperatur would not occur, for the absorption of radiant energy that causes it would be utilized in vaporizing water, tending towards a cooler temperatur. The loss of water in the leavs maintains a stream of water from the roots up which is necessary for the removal of the products of respiration (Babcock, 1912) and for the lifting of the absorbed mineral material to the leavs. Water is also necessary in - 20 - fotosynthesis. As Livingston (1911) puts it: "The total amount of transpirational water lost from a plant, for any given period, may be considered as a summation of the effects of the evaporating power of the air and of the radiant energy absorbed thruout the period, modified by certain secondary effects of these conditions and certain responses to other conditions." The ratio of the water income to that of the removal must not fall below unity for any considerable time in plants Which are not water storing. Quoting again from Livingston (1912): "The really crucial question with regard to any soil . . . is . . . at What rats, and for how long a time, can it deliver water to unit area of a Water absorbing surface?" That water is supplied in sufficient quantities during the most extreme conditions of summer that obtain in natur in this region is evident from this investigation, The opposit statement is true for winter, namely, that in very severe winters the removal of water from the exposed parts of certain plants is so in excess of the supply that too thuro drying and therefor death occurs. This same conclusion has alredy been workt out by Kihlman (1890) as the cause of the aſſic tree line. That the Water supply for ericads in Michigan peat bogs is actu- ally ample to their needs is clearly demonstrated by experimentation upon potted plants, for even under the very extreme evaporating power of the air on July 5, 1912 the maximum rate of transpiration was contemporaneous with the maximum evaporating power of the air. Condit- ions of atmosferic evaporating power in Michigan are never as high as those of Arizona, where Lloyd (1908) found that the fall in the rate of transpiration in ocotillo (Fouquieria splendens) occurd befor that of the maximum evaporating power of the air. Whether these results are really true expression of the behavior of rooted plants may be open to question, as Llºyd used cuttings to experiment with. It was found at – 21 - in the present investigation that on days of extreme evaporating power in Michigan that a decline in the transpiration rate in advance of the time of maximum evaporating power of the air did actually occur in cuttings but was not exhibited in potted plants of the same species • Such a check in transpiration is occasioned by What Livºton and Brown (1912) hav termd "incipient drying" in the course of which the evaporating menisci hav retreated into the pores of the cells, thereby not only decreasing the amount of the exposed surface but also greatly increasing the surface tension of these evaporating surfaces, which decreases the vapor tension and consequently the rate of vaporization (Renner 1910, 1911a and Patten, 1911). The increase in the concentration of cell sap which accompanies this check in Water removal further re- tards vaporization. A very serviceable pictorial presentation of the matter is given by MacDougal (1911). - The recent work of some investigators seems to withdraw the foun- efficient, function of the dations from the theory of the Astomates as the regulators of transpi- ration (Lloyd l308, 1912 and others). That closed stomates are effici- ent means of lowering transpiration has been demonstrated by many authors (Stahl, 1894, Burgerstein, 1904 and Delf, 1912). The closur of the stomates of evergreen plants during winter which has been demonstrated by several investigators, especially Stahl (1894), is an important factor in reducing transpiration at that season when the Water-intake is at best very low. The work of Lloyd (1908) on Fouguieria led him to conclude that the capacity of the diffusion of the stomates was well in excess of what would be required for the greatest observd transpiration rate. Dr. F. Darwin (Delf 1912:417, in a preliminary account befor the British Association concluded that if the stomates can be observed by a sufficiently delicate method that stomal movements are found to correspond closely with changes in the rate of transpiration caused by alteration in external conditions. In the present investigation, in which the method of relativ time of penetration of an oil was used to indicate the condition of the stomates, there was no evidence of a" closely regulatory" function of the stomates. The stomates opend in the morning in general in the diffused light of dawn, but the rate of transpiration showd no sudden rise but rather kept proportional to that of the evaporating power of the air. In the afternoon the stomates did not begin to close until after the beginning of the decline in transpiration. This was true both in potted plants and in cuttings properly cared for on days which Were not extreme. In many cuttings the closur of stomates seemd to be due to the shock of cutting rather than to any excessiv Water loss. All of the Wilted plants tested had their stomates closed, but in dried leavs the stomates were open, as the very rapid penetration of the xylol testified. The experimentation on plants in the field led to the conclusion that the stomates were open during the hours of sunshine and that altho the opening of the stomates preceded the rise of transpiration in the morning, the decline in transpiration set in in the afternoon befor the beginning of closing of the stomates. The rate of transpiration sunk more quickly to a lower level than the time it took the stomates to close could possibly account for. E X P E R I M E N T A T I O N = Materials and Methods. (of. Burgerstein, 1904) Thruout the study of this problem an experimental method was used which yielded numerical data. The experiments were carried on upon bog plants, principally Chamaedaphne calyculata (L.) Moench, obtaind mostly from First Sister Lake, about 2.5 miles west of Ann Arbor, Michi- gan and at Mud Lake in the northern part of Washtenaw County. Towards the close of autumn in l910 and 1911 plants of the ever- green ericads were potted and kept outdoors under prevailing conditions. During the ded of winter their transpiration was determined by enclosing the pot with an aluminum shell, devised by Ganong (1906), closed at the top with rubber dam and sealed. The water loss was thereby limited to the plant as controls repeatedly showd. The transpiration was deter- mined by successiv weighings on a beam balance sensitiv to 0.002 gram. Readings of weight to 0.01 gram, temperatur by mercury thermometer and thermograf, relativ humidity by wet and dry bulbs thermometers and gen- eral conditions of the weather were recorded. In addition to work with potted ericads during the Winter some three dozen plants were potted at First Sister Lake Ön June 1st, 1912, allowd to develop under bog conditions and experimented upon the first ſº Week of July. By far the greater part of the work, however, was conducted with cuttings. These were made from the plants at First Sister Lake, put in jars of water and immediately cut again and brot into the laboratory Where they were again cut. There the cuttings Were set in 2-holed rub- ber corks in bottles of distillºd water and sealed with vaselin. A ther- mometer, inserted in the other hole in the cork gave the temperatur of the solution. Work with controls prºved that the apparatus was Water Vapor tight. Usually about 1/2 hour was allowd for adjustment befor - 24 – measurements were commenced. Weighings were made at intervals of one, two or more hours according to the purpose of the experiment. Such experiments were seldom carried over 24 hours, except for special reºsons. The day of 24 hours of 100 minutes each was used in recording experiments, because of its obvious convenience. - Some plants which were transplanted into the greenhouse in Sphag- num did so poorly that no experiments were made upon them. Shoots that developt upon cut twigs kept in water in the laboratory or greenhouse seldom lived more than a couple of weeks and as their internal structur was not normal no experiments were performd upon them. It was found that different Chamaedaphne plants from the Chamae- daphne association transpired at virtually the same rate during the same experiment. Consequently that plant was taken as the basis for all comparisons and was included in practically every set of experi- ments. With the close of the experiment the leavs were detacted, placed side by side on white paper, coverd with a thin piece of glass and their outlines traced with a polar planimeter, by which means the leaf area was obtaind. After a little practisſ with this intrument it, Was found that successiv determinations of the same set of leavs did not vary by as much as 1/3 7. Accordingly the average of two determinations was used thruout the work. In cases where the stomates were present on the upper surfaces of the leavs – the rare exception in the plants used - the area thus obtaind was doubled. With the data thus obtaind, the results of each experiment were calculated With a K & E slide rule to a standard basis – the rate of transpiration in grams per hour per 100 square centimeters of leaf surface. These results were plotted on cross section paper and the comparisons made. As more than one determination for each plant was made the resulting curvs ought to approach a general similarity. Under the - 25 - of the curVs same conditions the similarity Awas striking. Thru dissimilarity of the resulting curvs it was possible to demonstrate both the effect of change of experimental conditions and to weed out aberrent plants - As the greater part of the work was concernd with relativ Values rather than with absolut values, the continued expression of the same con- clusion in the curvs was taken to uphold the contention and no conten- tion not so upheld uniformly is presented in this dissertation - During a part of the year 1912 the volume of the leavs was also determined by assertaining the amount of alcohol they displaced. Alcohol Was used in place of water on account of the large amount of air that the coatings of the leavs retaind when submerged in it. The results were calculated on the basis of water lost per hour per one cubic centi- meter of volume. This was done in order to incorporate the results obtaind from plants, the difficulty of determining the leaf surface of which, would otherwise hav renderd it virtually impossible. The cor— relation of volume and leaf surface were irregular. With leavs of about the same size and thickness the amount of water lost varied about the Same for either case. In plants of Chamaedaphne from different plant associations, where both size and thickness of the leavs varied, it did not usually appear that volume was any constant function of the leaf 3,1288, a While it is recognized that the measured leaf area is not the area of the real water-loosing mesotyl cells, it is believd that it fur- nishes a satisfactory basis of comparison attaind without the excessiv determination of the difficulty that would attend the Aactual area of the surface abutting on? Yºº the intercellular spaces. The leaf surface, moreover, is the area thru which the diffusion into the outer air takes place. At the close of many of the experiments a section of the smallest part of the stem below any transpiring organs was cut out, perservd in glycerin-alcohol, latter imbedded in rubber-paraffin, sectiond, staind with iodin green and mounted. Camera lucida drawings were made with which to determin the actual area of the conducting system by means of the polar planimeter. By means of the lithium nitrat method, which consisted of cutting off stems under a .005 % solution of Li (NO3)2 in water, removing after certain intervals, cuttings the stems into one centimeter lengths and testing in the spectroscope for the presence of lithium, the rate of conduction was determined for a number of stems under different conditions. Experiments on Transpiration during the Winter- General discussion: During Winter the transpiration of the plants of the region is reduced to a serviceable minimum which, however, is not zero. For herbaceous plants this minimum is lower than for shrubs or trees. It is probably never actually zero even tho no leavs are present. It is certainly very low in seeds and underground roots and bulbs, which tide the species over the unfavºie season. No experi- mental Work was undertaken to determin the water loss of these plants because there would be no comparison with the shrubby ericads which retain their plant body thruout the winter. The purpose then of the winter experimentation was to obtain a knowledge of the transpiration of the shrubs and trees and to compare that of the leaf-possessing ericads with that of the leafless shrubs, under the Winter conditions outdoors and under laboratory conditions Which simulated the severest conditions which could naturally obtain during the Winter. Experimental work was carried on both with potted plants and with cuttings, indoors and outdoors, and the data which follows givſ an – 27 - idea of the natur of the results from which the conclusions are drawn. In the cases of shrubs, whether leavs are present or not , there is always a medsurable amount of transpiration even during the coldest weather. (Cf. Kusano 1901 and authors cited by him, also Burgerstein 1904). The actual amount is often very small and could not always be measured to within 0.005 gram with the balance used. Experiments upon potted plants, outdoors, Jan 7–15, 1912. 7. 16.85k 8. W. 93 9. 8. 55 16 - 77 10. 7. 48 11. 7.62 16. 6.8 l2. 9. 10 16, 15 13. 9.93 Transpiration. Andr.” Andr. V, m. V.m. %. 4300 4301 4302 4303 -------------------------------------------------------------------- ... O 374 .0005 .0018 .0183 .0912 • 1420 - O 592 Cham. Cham. 450 4 4505 • 00:28 +. OO74+.014.5+... O 225+. OO 31 +: 0002 ... O 302 • OO74. • Ol.98 .01.46 - 00:40 .0035 ... 02:52 - 06:29 . 0120 ... O 586 .0257 - OO 97 .0054 - O'778 .0000 +.0025 - º ( 3: In conſtructing # * .0491 - 014.9 . () 608 - O 175 ... O 850 - 0.282 .0758 - O 215 ... O 455 - 00:55 ... Olć5 . O098 • 0280 +.0117 . OO 39 • OO 18 . OO 36 . OO27 • 00:29 ... 0012 .0074 - 0008 . OOO3 +, 0.002 + 0005 - OOO6 • 0.042 • OO 95 .0025 • 004.5 ... 00:24 - 0.227 .0000 -r, 0.088 -17. -15. -15. _15. -15. -13. –l4. -13. -25. –21. S110 We Srl O.W. clear, Windy cloudy, clear, Windy. cloudy . Cloudy. Cloudy. Slirl clear this and the following tables abbreviations Will be used for the name of the plant which will usually be self- explanatory, viz. "Andr" = Andromeda glaucophylla, "V.m." = Vaccini- liſh Iſlä CTO Q&rºpuſil, "Cham" = Chamaedaphne calcyculata. "k" standing after or above a column of figurs ineans "o'clock" and indicates the time of measurement based upon days of 24 hours of 100 "minutes" each respectivly. Figurs of transpiration indicates the grams of waterloss per hour per 100 cm2 of leaf surface. Temperatur is 90. ) Inspection of the graf's obtaind upon plotting these figurs shows tha\, Andromeda transpires at a lower rate than Vaccinium macrocarpum and Chamaedaphne at a lower rate than Andromeda. Transpiration is not indicated during a heavy snow storm even tho the plants are protected from the snow. Transpiration is increast by wind, sun and higher temperatur and decreast by increasing humidity - The following table presents the same facts and it is not necessary insert the several others that bear out the same results, on account -of-needless repetitions- Experiments upon potted plants, outdoors, Jan 15–17, 1912. Transpiration. Cham. Cham. Cham. V, m. Andr. Andr. Jan. k #4292. 4295. 4291. 4295. 4299. 4298. Temp. Weather. 13. 16.40 - 0134 .0057 .0000 .0562 +.0122 +.00.91 –12. pt. clay. 91 % lº. 9.98 .006.3 . OO 32 .0056 .0095 - 0.177 - 00:50 -10. cloudy. 54 16.80 .0065 • OO 21-r, OO47t.0125 - 0000 - 0000 - 8. lt snow. 85 15. 8.25 +.0014 .0013 r.0041 .0000+.0038 .0028 –13. clearing 77 16.45 .0013 .0000 .0078 .0000 .0000 .0000 –17. clear 48 l6. 8.47 .0000+.0004 .0000 .0000 .0000 .0000 –16. clear 50 46.03 .0161 .0188 .0338 . 1680 .0546 .0487 -10. (-5) iſ 68 17 - 7 - 48 • OO29 - 0013 .0021. 20041 - 0077 - 00:50 –5. Cldy. 67 % ll. 25 rain set in and the weight of all the plants increast. ------------------------------------------------------------------------- Transpiration experiment upon a cutting (Chamaedaphne 4389)0**** Feb. 27. 1912 13.45k 3.59 (solution .018 g/hr/100 cm2. temp. ) 16.25 0. 5 .008 l6.95 -0.5 .004 28. 8.70 -5.0 . . 006 12.05 1.0 • O27 19.77 - 1.0 • 006 29. 9.85 –2. • 008 Transpiration experiments upon Cuttings, outdoors, Mar. 1-2, 1912. sol. cham. cham. Outdoors - k temp. 4420. 4:421. Temp. Rel. Humidity. Mar. l. ll.98k 0. 59 .0053 –2.5° 49 % 20. 20 -1.0 .0078 .0000 -8.0 72 Mar. 2. 9.05 -0.0% .0019 - 00:42 l.0 82 11. 58 0. 5 . OO97 - 00:42 3.0 -- 16. 27 0. . OO77 - 0.090 —5.0 60 ( * a minus sign in front of a temperatur of zero C. signifies that the water is frozen, whereas the , absence of a sign would mean that the water is in a liquid state. outdoors Transpiration experiments Aupon a potted seedling Picea mariana. A potted seedling of spruce which was experimented with on Feb. 3-5, 1911, gav a curv which was similar to those obtaind by plotting data from ericads for the same period. The amount was small but can not be compared directly with that of the ericads in the absence of the leaf area. A very conservativ estimate of the leaf surface of the spruce would indicate that its rate of transpiration is quite a little lower than that of Chamaedaphne. Transpiration experiments on cuttings run outdoors in Winter, Feb. 10-12, 1911. First period. Second period. -------------------------------- Larix laricina (4090,4091 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4092) .00020 .00025 g/hº/100 cm? Chamaedaphne calyculata (4095,4094) ... O 152 ... O 158 Cephalanthus occidentalis (4095, 4096) - 00:50 -- Nemopanthes mucronata (4097) .000016 .000025 Acer rubrum (4098) - - 0019 • 00:45 (The first period represents the 24 hours following Feb. 10 at 13.55k and the second the 24 hrs following the first period.) - 50 - The temperatur during the first period varied from 1-0 to -14.9 C and the weather was clear. During the second period the wind was stronger and the temperatur extremes were -1. and 5.9 while it was mostly cloudy. This experiment show how much the transpiration rates amount to in winter under average conditions of "nice" weather. The ever- green Chamaedaphne shows a rate distinctly higher than that of any of the others. The typical northern bog shrub, Nemopanthes, here, as repeatedly exhibits a transpiration much lower than that of a southern swamp shrub, Cephalanthus occidentalis. The transpiration from the deciduous conifer, Larix laricina, is decidedly lower than that of the deciduous hardwood, Acer rubrum, during the winter. The loss of leavs, therefor is a very decided factor in reducing the rate of transpiration during the winter. Transpiration experiments on cuttings, outdoors in Winter, March 3–8, 1912. Larix laricina (4440), Betula pumila (4441) and Chamaedaphne calyculata (4442). The results of this series of experiments will be found exprest in grafic form in Plºto \ , and the values obtaind therefrom. The graf's show how very low the transpiration is during the winter and how evident it is that the deciduous habit is a well-developt xerofy tic adaptation. The water loss is greater during the daytime, shorºtho it is, than during the night and increases rapidly with increase of temperatur, more rapidly than temperatur, other things being equal, be- cause the evaporating power of the air increases in proportion to the absolute humidity with the temperatur if other conditions are equal. Consideration of these data clearly indicate that the transpi- ration is very low in winter and furthermore, with scarcely an ex- ception, the rate of water loss is much greater (two to fifteen times) in the evergreen ericads than in the leafless shrubs and trees. When the very much more exposed position of the leafless shrubs and trees is taken into account, the difference in the rate of transpiration in natur is accentuated. The mere position of the ericads, low down near the ground for the most parts servs to reduce Water loss. This same relation holds among the ericads/ themselvs, namely, that the greater the rate of transpiration under given conditions the more protected a position that species grows in. For example, Chamaedaphne transpires at a lower rate than Andromeda and it than Vaccinium macrocarpum and Chamaedaphne grows higher than Andromeda which in turn is higher than Vaccinium. Yapp (1909) has shown that the nearer the ground in a closed association the smaller the evaporating power of the air. These data support the well-known facts that transpiration varies directly with the temperatur, inversely with the relativ humidity, and is greater in daylight than in darkness. The latter may possibly be almost entirely included in the two former as the absorption of radiant energy during the day would increase the temperatur of the leaf were it not used up in augmenting transpiration. Other things being equal, transpiration shud always be higher in the day than in the nite. Only rarely does the rate of transpiration excede .01 g/hr/100 cm2 in any of the plants experimented with under winter conditions. With the exception of Vaccinium macrocarpum the rate is more often less than .005 than above it. In the leafless Shrubs it is usually below .001 and not infrequent in hardly more than Within the power of measurement with the means employed. This, of course, evidences the advantage of the deciduous habit in reducing transpiration in winter. - 52 - ( During stormy weather it is difficult to allow a real exposur to the Weather and then ºbe-able to neisure transpiration by weighing, ! but repeatedly when preparations were shielded from snow or rain, medsurement showd an increase of weight beyond that of a control. This Was noticed in Chamaedaphne and Andromeda Whose leavs are coverd with scales and hairs, respectivly, beneath. The absorption helps replenish the saturation deficit of the leavs and so at least in a small) measur alleviates the demands upon the root system at a time of year when absorption is at best difficult. A factor of geografic distribution is evidenced in that under similar conditions, a northern bog shrub loses water at a much lower rate than does a southern swamp shrub. Experiments upon the Transpiration of cuttings run in the greenhouse, Dec. 2-12, 1911. During the early part of Winter a number of experiments Were peº- formd upon cuttings in the greenhouse. The conditions, obtaining there, resembled extremely warm spells in Winter, except that the relativ humi- dity was higher. The temperatur averaged about 17°, on sunny days it might go as high as 30 in the sun and 110 was the lowest temperatur I’60 Orded , Under these conditions it was found out that the rate of transpira- tion was rather low and yet it was noticeably higher than that outdoors, both in the deciduous and evergreen shrubs. The presence of sunshine, other external conditions being equal, was the most potent factor in increasing the rate of transpiration. Of the three ecºnads experi- mented upon, Vaccinium macrocarpum and then Andromeda showd higher rates than did Chamaedaphne. All of these were higher than leafless twigs. - 53 - Per unit area of leafless twig surface, bog shrubs lose less water than do the bog trees under the conditions of these experiments. Bog shrubs, however, are more subject to winter killing in a severe winter in this latitude unless protected by snow. This would seem to indicate the xerofutism of the bog trees was in general more efficient than that of the bog shrubs, under extreme winter conditions or, on the other hand, that their means of water renewal was more efficient. Transpiration of cuttings run in the greenhouse, Dec. 2–5, 1911. Chamaedaphne Andromeda Wac. macroc. 4311, 4312. 4315,4314 4315,4316. Temp. R. H. Weather ------------------------------------ ------------------------------ k g/hr/100 cm.” oC 7 Dec. 2. 10. 25 - - 16. 74. clay 15.00 ,052 ... O 39 • 109 14. 89 clay 20.00 .024 - 024 ... 100 16 . 81 ſº Dec. 3. 8. 25 .027 .040 .035 14. 79 pt. Cldy. 13. 50 ... O 55 ... O 90 • 120 17. 74 º º 19 - 50 • 028 ... O 57 .053 17. W9 ff ff Cham. Cham. Acer. Nemo. Larix. Salix 4,522 4524. 4.317 4519 4520 4527 4.325 4.325 4518 4321 4328 DeC 4326. Temp. R. H. 5. 15.50 170 78 % }. 7.25 - 057 .058 .021 .010 .058 ... 012 17 79 7. 7.25 - 0.26 .037 .013 .005 .015 • 009 19 69 16.75 - 071 - 090 .025 - 01.1 - 0.51 • 0 14 17 81 8. 7.25 - 0.23 - 027 .010 .005 - 0.10 .009 17 76 16. 50 .036 - 04.4 .012 .005 .012 .014 lá. 91. 9, 8.25 - 025 - 027 .008 .004 - 008 - 006 19 79 The plants of Chamaedaphne 4322.4325 were collected in the Chamaedaphne association, while Nos. 4524. 4325. 4326 were collected in the Larix association. The other plants are Acer rubrum, Nemopanthes mucronata, Larix laricina and Salix pedigellaris- - 34 - 12. 15. 58]: 7.02 18. 20 7. OO 16. 55 7. 57 15. 17 4.329 – 4351 ,051 .027 .015 .027 • O25 • 0.31 Transpiration of cuttings in the greenhouse Dec. 7–12, 1912. Chamaedaphne Chamaedaphne Chamaedaphne (Carex Assoc) (Cham. Assoc) (Larix Assoc) 4332 – 45.34 4355 – 4337 Temp. R.H. Weather ---------------------------------------------------------------------------- - - .02 - 0.25 ... O 15 - 0.25 .021 - 0:28 150 87% O. O.22 15 88 clay - 024 18 87 ºf .014 15 88 smoke .023 18 82 Cldy. , 0.21 16 79 º .029 17 81 º Experiments showing the influence of solution temperatur upon transpiration. To determin the influence of the temperatur of the solution from Which the cutting was taking water upon the rate of transpiration, the following experiments were made in the laboratory. Experiments upon the transpiration of Chamaedaphne cuttings, Feb. 27– 28, 1912. in the laboratory. (The temperaturs indicated in the table are those of the solutions in which were the cuttings. The temperatur of the room varied between 21 and 249, the rel. humidity 20 to 45 %. Over the radiator the temperatur was 28 to 38° and the rel.hum. 4 to 20 %.) Room. Cham 4581 4585 Radiator. Cham. 4584 Cham. 4583 4.588. 4587 * * * * * * * * - - - - - - - - - - - - - - - - - - * * * * * * * * * * * * * - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -- Feb. 27. 10 - 32 l3. 32 16.00 18 - 70 8. 38 ll. 80 19. 28 Cham. 4582 4586. 0. 50 0. 5 - 055 O - 5 - 055 O - 5 - 0.49 6.0 .046 2.0 - 08.4 1.0 - 082 - 35 - Experiment upon the transpiration of Chamaedaphne cuttings on the radiator in the laboratory. (This experiment was conducted on the radiator, the temperatur of the air at the level of the leavs being between 31 and 35°, while the relativ humidity varied between 14 and 16 %. ) Chamaedaphne Chamaedaphne 4415, 4419. 44lé. Mar. l. 9.00 3.0° 450 1912. 11.75 0.8 .065 44 .221 g/hr/100 cm.” 15. 27 0.8 .075 40 - 225 Experiment on the transpiration of a Chamaedaphne cutting (44.39) in the laboratory, March 3–6, 1912. Chamaedaphne 4439. - Temp. R. H. k Sol . temp. transp. Mar. 3. 1912. 9.65 170 22° 35 % 12.70 20 .046 22 45 16 - 85 21 .. 5 .040 25 54 20. 50 18 ... 0.40 18 55 4. 7.65 18 ... O 52 22 50 13. 60 22 ... O 58 25 28 5. 8, 55 19 .049 18 25 18.25 25 . O67 25 28 6. 8. 40 21. ... O 54. 25 19 Experiment on the transpiration of cuttings in the laboratory, March 5–6, 1912. Larix Larix Chamaedaphne 4490,4491 4492,4493 4494. Mar. 5. 9.00k 199 0,5° 0. 50 14. 45 22 - 0.25 0.2 - 051 0.2 .060g/hr/100 cm2 18.72 23 - 021 l =0 .025 l.0 - 0.62 6. 8.72 21 .015 1.0 .015 1.0 .016 - 56 - A study of the graf's of the data obtaind between Feb. 27 and Mar. 6, 1912 brings out the following points: High temperatur causes high transpiration but if the temperatur is high enuf to kill (about #5°) the transpiration falls suddenly from the high level to a low amount, then rises to a higher level following which the amount of evaporation varies with the evaporating power of the air. Generally the rate of transpiration under given evaporating power of the air isºgreater at first from the colder solution, but after a short time it becomes less and less the colder the solution. A warming of the cold solution up to room temperatur or above is followd immediately by a rise in transpiration, clearly indicating that Chamaedaphne Can take in Water faster in a warmer solution. On Feb. 28, with a temperatur constant to within 20 and a relativ humidity constant to within 5%, in Chamaedaphne plants which were run in the laboratory with light about .01 % of sunlight, and not at any time exposed to direct sunlight, the rate of transpiration was very noticeably higher during the diffuse daylight ( .071 and .083 ) than in the periods of darkness befor and after it. During the night following with the temperatur constant but the relativ humidity drop- ping slightly the transpiration of these same duplicates decreast to •046 and .060 respectivly. Experimentation upon Chamaedaphne 4439 with 3. decréing temperatur and constant relativ humidity resulted in a gradual lowering of the rate of transpiration and a decrease in the relativ humidity without temperatur level changes resulted in an in- Crease in the rate of transpiration. In the course of these experiments cuttings were made during the cold, snowy weather of February and March 1912 and subjected to diff- erent conditions in the laboratory. Plants of Chamaedaphne consti- tuted the bulk of those used. The laboratory conditions of temperatur and relativ humidity were more extreme than these plants are ever in Winter subjected to in natura and often compare with summer conditions. To determin the influence of a cold spource of water supply, twigs were set up in water in bottles and set in a snow mixtur, which maintaind the temperatur of the solution at freezing. At the same time other sets were carried on with the temperatur of the solution that of the room. These experiments were repeated under the very severe conditions obtaining over a steam radiator, above which the air tempe- ratur varied from 58 to 500 and the relativ humidity from 4 to 20 % | When the temperatur of the solution was allowd to become hot, transpi- ration proceded at a very rapid rate for a time until the tissue was killed at a temperatur of from 42 to 469, after which the transpiration fell to a low amount without a corresponding drop in the evaporating power of the air. The curv which is obtaind from these results may be called the defith curv. It is similar to those obtaind by Bose (1906) in his experimental work on death in plant tissues. After the markt drop the rate of transpiration increases and then fluctuates with the evaporating power of the air but does not exhibit the decided increase which access of sunlight causes in living twigs in winter. Other twigs set up and maintaind in cold water under the evaporat- ing conditions over the radiator showd that the greater evaporating conditions resulted in greater transpiration over the radiator than in the room, but the average rate of transpiration was very little in excess of that of twigs in the room with solution at room temperatur. This shows clearly the retarding influence of cold soil water and in addition the ability that these plants hav of withstanding a much severer àeral condition of high temperatur and low relativ humidity for a much longer time than they are ever subjected to in natur. The forgoing conclusions are based upon plants of Chamaedaphne growing in the Chamaedaphne association. As has been previously - 58 - mentiond, such plants vary but very, very little among themselvs. Chamaedaphne, however, is not limited to the Chamaedaphne association but grows as an invader in the Carex association and persists as a relic in the Larix association. When the results were averaged together, it was found that, altho they supported the same general laws, there was a higher amount of variability between individual plants from the Carex and Larix associations than from the Chamaedaphne association. Under the same atmosferic conditions the transpiration rate of plants from the Carex association was at a decidedly higher level, while plants from the Larix association were at a slightly lower level than those of the Chamaedaphne association. The lowering of the solution temperatur was decidedly more effectiv in reducing the transpiration of plants of Chamaedaphne from the Carex association than in those from the Chamae- daphne association. The soil water temperatur is higher in natur in the Carex association (Transeau 1905-6 and verified in this work) and the plants may hav become adjusted to it and carry over the ability thru the winter. summary of the Experiments showing the relation of solution temperatur upon transpiration. (In the summary which follows, the name and collection number of the plant is given, after which the rate of transpiration is exprest in grams per hour per 100 square centimeters of leaf surface. Determina– tions at room temperaturs, which vary from 18 to 25° and those made with the solution at or very near freezing are separated in the columns. The figur in parentheses which follows a figur expressing rate of transpiration, indicates the number of readings that are averaged ſº in ing arrivp, at this figur. ) – 59 - Relation of the solution temperatur to the transpiration, 1912 Experiments performd in the room with the solution at Room temperatur, Freezing temperatur. ------------------------------------------------------------------------- Feb. 27. Chamaedaphne #4381 .060 (5) #4582 .055 (3) Chamaedaphne #4385 .069 (3) #4386 .048 (3) Mar. l. Chamaedaphne - - #4412 .044 (3) #4413 .056 (5) Chamaedaphne #4416 .056 (2) #4417 .045 (2) Mar. 5. Larix laricina #4490 .021 (2) #4492 .O.30 (2) Larix laricina. #4491 .025 (2) #4493 .026 (2) Mar. 12. Chamaedaphne (Carex assoc.) #4569 .080 (2) #4564 - 074 (2 #4565 .061 (2 Chamaedaphne , Cham. assoc.) .071 (2) #4565 .061 (2 #4570 Chamaedaphne (Larix assoc.) .042 (2) #4566 .048 (2) #4571 #4568 .O.35 (1) Experiments performd over the radiator with the solution at * Radiator temperatur, Freezing temperatur. Feb. 27. Chamaedaphne - #4383 . 117 (5) #4384 .057 (3) #4587 . 105 (3) #4388 .089 (3) Mar. 1. Chamaedaphne #4414 .201 (3) #44.15 .052 (5) #4418 . 144 (3) #4419 .072 (2) Averaging all these results under suitable headings we obtain the following figurs: under room conditions, - - warmer solution Golder solution Chamaedaphne (Chamaedaphne assoc.) .062 ... 0.54 Chamaedaphne (Carex association) ... O 80 - 068 Chamaedaphne (Larix association) .042 . 042 Larix laricina (Larix assoc.) - 0.22 ... O 28 - 40 – under radiator conditions, --------------------------------------- Chamaedaphne (Cham. assoc.) • 144 - ... O 68 Inspection of this assemblage of data wherein the rate of tran- spiration with cuttings was determined under the same air conditions but with temperaturs of the solutions at distinctly different levels, shows that the colder the temperatur of the solution from which water is absorbed the lower is the rate of transpiration. This effect, how- ever, is not nearly so prominent as one might at first think. The control was much less perfect in deciduous twigs than in leafy ones, as the data obtaind from Larix in this experiment and are occasionally greater from the colder solution. That this control was more promi- nent in leafy than in leafless twigs suggests that transpiration exercises the fundamental control and that a slight lowering of the rate of transpiration from a colder solution is in proportion to the amount of energy required to warm the colder water up to the room temperatur. These bog plants are subjected to the extremes of temperatur of soil water maintaind in the laboratory (not over the radiator) – more frequently the lower one – and this range is well within their fysio- logical ability. The same conclusions could not hold for ordinary plants that can not stand such a lowering of soil water temperatur, as shown in Sachs's (1860:124) famous experiment on Nicotiana and repeatedly demonstrated on other plants, as, for example, Fucksia and TT - goleus. Leafless twigs hav occasionally shown a higher rate of transpira– tion from the colder solution but this is probably due to the stimu- lation that is the first effect of application of cold (Bose, 1906). This stimulation increases the rate of transpiration over that of a plant not so stimulated for a while but later the rate becomes – 41 – much less in the one from the cold. This period of stimulation has lasted an hour in plants of Fucksia. In leafless twigs, where the regulation of transpiration is less perfect, it has continued all day. In no case during the course of this investigation did this higher rate from the colder solution continue for more than 10 hours. Warming up the solution was uniformly followd by a gradual rise in the rate of transpiration. This is true of both leafy and leafless twigs but is more striking in the leafy twigs. General Summary of the Winter Work on Transpiration. - - ------ From the experimental work performd during the winter on bog plants it is redily seen that there is a continuation of water loss thruout the winter. This loss takes place at a very low rate during low temperaturs. Thruout the course of the experimentation the transpiration was found to obey the same general laws that govern the evaporating power of the air. Water loss continued to take place 6 Ven when the water was frozen around the stem and continued to do so. Either this water loss was a permanent drain on the water content of the stem or as the experiments on conduction showd there was a Certain amount of renewal from the fºozen solution far faster than diffusion go account for. Whethe, a plant can obtain water directly from an ice surface is a matter for ſysicists to determin. It has been shown that roots can absorb water even when the temperatur is below freezing by Kosaroff (1897) and others. The amounts are small but are usually sufficient to satisfy the needs of the plants. In natur the ground, tho often frozen to a slight depth, is usually protected by a snow cover during Winter. The spaces between the snow particles are saturated with Water vapor. This produces a blanket effect and greatly reduces the temperatur changes underneath, tending to keep the temperatur near the freezing point . - - 42 - The upright position of the leavs is a xeroflytic adaptation to receiv a minimum of the direct sunlight to which they are exposed. The mere position of the species of evergreen ericads is in itself in line with xerofily, for the species that hav the greatest ability to transpire are most protected in their natural environment. Experimentation upon the Rate of Conduction during Winter- Experiments of Feb. 22–23, 1912 upon Chamaedaphne in the laboratory. Hours Rate of conduction 0. 5 4.0 cm/hr. l.0 3.0 l. 5 4.0 4.0 2.0 5. 5 2. 5 5. 6 2.8 5. l. 5. O 3.0 4.5 5. 6 Experiments of Feb. 24, 1912 upon Chamaedaphne in the attic with a temperatur just above freezing. Hours Rate of Conduction 1, 5 2.7 cm / hr 3. 5 2. O - 43 – Experiments of March 5, 1912 upon the conduction of Acer rubrum, Spiraea salicifolia, Betula pumila, Chamaedaphne calyculata and Larix laricina, under the conditions indicated. Acer Spiraea Betula Chamaedaphne Larix Hours. rates of conduction. ------------------------------------------------------------ the room. 2. 5 l. 2 2. 1 2.5 2.7 1.7 cm/hr 6 - 5 0.6 2.0 2.8 2.8 l. 2 10.6 0. 5 - 2. l 2.2 l. 3 In the room with the temperatur of the solution near 0°C 2.7 O.7 l. 4 1.6 2 - 2 2.5 7... O 0.6 l. l 2.5 2. 5 1. 6 ll.0 0.6 - 2. l 2. 4 (3) 1. 5 Outdoors, temperatur below freezing. 2.8 0.4 l.0 l. 2 l. 1 1.0 7. O. 5 - 0.7 - - 8.6 O - 5 - - 0. 5 O - 5 ll.0 0.4 - - 0.4 0.4 In inspection of this table shows that under the same atmosferic conditions of evaporation the rate of conduction, as measurd by this method, is only a little less in the deciduous bog shrubs than it is in the evergreen Chamaedaphne. In the deciduous hardwood tree, Ace rubrum, it is even still lower. The rate of conduction was noticeably higher from the colder solution in Larix, especially at first. Under outdoor conditions Ager shows a lower rate than either the deciduous Larix or the evergreen Chamaedaphne right from the start. Experiments of March 5, 1912 upon the conduction of Chamaedaphne calyculata and Larix laricina under the conditions indicated. Started at 8.00 o'clock. – 44 — Chamaedaphne calyculata Larix laricina ---------------------------------------------------------------------------- In the room with the solution at room temperatur. 3.5 hrs 3.0 cm/hr. 2. 7 hrs 5.7 cm/hr 5.5 2.7 5 - 5 2.4 7.2 - 7.2 2.5 9. l - 9. 1 l. 8 In the room with the solution at freezing temperatur. 5, 6 2.5 5. O 3. 8 5. 6 2. 1 5. 2 2. 6 9. 1 2.6 9. 1 1. 8 On the radiator with the solution at its temperatur (39 to 45°) l. 2 7.5 1.8 5.9 5.7 4. 5 Outdoors with the solution near freezing. 3, 6 2.4 2.9 2.4 5.8 l. 2 5. 4. 2.0 7.8 1.4 (2) 9. 5 0.8 9.6 l, l Outdoors with the solution frozen. ... 7 ... 5 .5 (2) ... 4 The results of this experiment show that the rate of conduction of the leafless twigs of Larix doesn't differ very much from leafy twigs of Chamaedaphne under the same conditions of evaporating power of the air. There is a greater amount of rise of the lithium nitrate in the stems frozen in the solution than mere diffusion could account for. With the solution at a high temperatur a high rate of conduction was exhibited but the discoloring of the solution when the temperatur rose to 429 indicated the killing of the stem ends. - 45 – Experiments of March 10, 1922 upon the conduction of Chamaedaphne calyculata from different associations under conditions indicated, in the greenhouse. C h a m a e d a p h n e C a 1 y C u l a t a - from Carex Association Chamaedaphne Association Larix Association. ----------------------------------------------------------------------- In the greenhouse at its temperatur. 2.5 hrs 5. 5 5. 4. 5.4 cm/hr 5. 6 - 2. 1 3.5 5. 6 - 2 1.5 5.4 5. O 2. l. 5.5 3. 3 In the greenhouse with solution at freezing temperatur. 2.4 2.7 5.9 4.8 3.7 5. 1 5. 5. 1 6 - 5 — 8-l —2.7 -- —2.6 2.8 3. l 3. 4. Outdoors, with the solution frozen during the first 4 hours. 2.5 l. 2 l.0 2. 6 3.8 l.0 l. 4. l. 1 6. 4 — 0-8 O. 8 1. 3 l.0 l. 1 1. 5 Experiments of March 12, 1912 upon Chamaedaphne calyculata. In the laboratory with the solution at room temperatur. 2. 2 hrs 5.8 (3) (no. of 2.0 (2) 5.0 (2) cm/hr 3, 2 4.5 (5) twigs) 5.9 (3) 5.7 (3) 4. 9 2.9 (2) 2.9 (2) 2.8 (3) 6 - 2 2.7 (1) _2.8 (1) 2.7 (2) 5.7 (9) 5.0 (8) 5.5 (10) In the laboratory with the soultion near freezing temperatur. .0 4.3 (2) 5.2 (2) 6.5 (2) 2.9 5.5 (2) 4.2 (2) 4.9 (3) 4.8 2.8 (2) 2.8 (2) 3.4 (2) 6. l 2.3 (1)– 2.8 (1) 2.8 (1) 5.4 (7) 5.9 (7) 4.7 (8) These sets show that the rate of conduction is greater when the Saturation dericit of the air is lower. The rate is more uniform from the Garex and Chamaedaphne associations than from the Larix association. Plants from habitats where the soil water temperatur is naturally lower hav a greater ability to conduct water from a colder solution. - 46 - Summary of the experiments upon the relation of the solution 1100I) -------------- --- temperatur to the rate of conduction, winter- under room conditions. --------------------------------------------- - - - - - - - - - - - - - - - - - - - - - - - - - - - Feb. 24. Chamaedaphne Feb. 25. Chamaedaphne l Feb. 27. Chamaedaphne 2 Mar. l. Chamaedaphne l Mar. 5. Acer rubrum O Spiraea salicifolia 2 Betula pumila 2 Chamaedaphne 2 l 2 2 2 5 5 -> :8. ( 2 ) : ( 2 ) Larix laricina Mar. 5. Chamaedaphne Larix laricina Mar. 10. Chamaedaphne (Carex assoc.) Chamaedaphne (Cham. assoc.) Chamaedaphne (Larix assoc.) 3 Mar. 12. Chamaedaphne (Carex association) Chamaedaphne (Cham. assoc.) Chamaedaphne (Larix assoc.) Mar. 15. Larix laricina Chamaedaphne ( 2 ) : (5) (4) (9) (8) (10) (9) (2) 552 - (8) (9) (1) - i ( 7 ) i ;55 Averaging these results under suitable headings We obtain the following figurs. Warmer Solutions freezing solutions Chamaedaphne calyculata cm/hr. cm/hr (Chamaedaphne association) 5.1 (29) 2.5 (35) Chamaedaphne calyculata (Carex association) 5. 2 (13) 3. 1 (12) Chamaedaphne calyculata (Larix association) 5. 5 (14) 4.3 (12) Acer rubrum 0.8 (3) 0.6 (4) Spiraea salicifolia 2. l. (2) l. 3 (2) Betula pumila 2.4 (3) 2.0 (3) Larix laricina 5.0 (17) 2.7 (19) Under radiator conditions. warmer solution colder solution Chamaedaphne calyculata 3.0 {3} 2.8 (9) Larix laricina 5. 1 (4. - 47 - Thruout these experiments the plants were subjected to air conditions which in the laboratory were fairly constant (27 to 45 % relativ humidity and 18 to 249). The temperatur of the solutions was however different – one set being kept at approximately 20° while the other was near freezing, at about the temperatur of the bog water whenever it medited during the winter. The results obtaind from these experiments were subject to considerable variation but in general the rate of conduction was greater from the warmer solutions. That there should be so little difference in the rate of conduction with these two extremes of solution temperatur (20 and 9") is notable. It argues decidedly for a control of the rate of conduction by transpiration. Because more heat units are required to warm up the colder water the transpiration of the plants in it ºº is slower. Experiments on the rate of conduction in different evergreen ericads and its relation to transpiration. Experiments of April 4, 1912 upon Andromeda glaucophylla and Chamae- daphne galyculata in the laboratory. Andromedia Chamaedaphne Time conduction transpiration conduction transpiration o.40 hrs 15.1(3/hr. 10.8 (2) 1. 70 5.3 (4) 5.6 (2) 2.08 5.1 (6) 4. 2 (3) 5. OO . 250 . 140 7.5 (13) .350T 5. 9 (7) . 140 Similar experimentation was carried on the following day with Chamae- daphne and Vaccinium macrocarpum and on the next day with Andromeda and Vaccinium. The average results are summed up in the following table. - 48 — Summary of the experiments of April 4–5–6, 1912. Rate of Conduction. (centimeters per hour) Chamaedaphne Andromeda Vaccinium macrocarpum. 5.9, (7) 7.5 (13) - 4.9, (9) - 8. 3 (12) - ll. 1 (12) 16. 3 (11) ºver. 5.34 8. 4-5 12. 11 ratio. l.00 1.58 2. 27 Rate of Transpiration (grams per hour per 100 cm?). . 140 (2) . 230 (2) - ... 101 (2) - . 501 (2) - .290 (2) . 527 (2) 8, Verºs . 121 . 260 . 414 ratio. 1.00 2. là 3. 42 Both the rates of conduction and transpiration are higher in Vaccinium macrocarpum during the Winter than in Andromeda glaucophylla and higher in the latter than in Chamaedaphne callygulata. relation between the Experiments upon the Arate of conduction and transpiration in Chamaedaphne callygulata under different conditions. All of the experimental data which bore upon this point was assembled under appropriate headings and is presented in the following table. In each case the rate of transpiration is divided by the rate of conduction and the resulting factor expresses the number of grams of transpiration which º is equivalent to 1 cm of conduction. - 49 - C h a m a e d a p h n e C a l y C u l a t a . -------------_*: * * * *arch 3 ºrch 5, 121°. *::::::... ** = .083 #2 = .000 - - *::::::...inc # = .029 # = ... O 25 - - ...,n #2 = .020 #. = .009 #4 = .004 - March 12, 1912. C h a m a e d a p h n e c a l y C u l a t a . Carex assoc. Chamaedaphne assoc. Larix association. ---------------------------------------------------------------------- Laboratory 2080 = no -071 = 2042 = room temp. 5.7 .022 5.8 - 0.19 5. 5 ... Olſº Laboratory .067 — -0.6.1 - •042 – sol. freezing 3.3 T .020 # = .016 # = .009 To answer the question as to the relation of transpiration to the amount of conduction by the lithium nitrate method, the data obtaind from simultaneous experiments of transpiration and conduction was assembled and has been presented above. The average values of all specimens under the same conditions during a day is used as a unit of comparison. The relation is exprest by dividing the rate of tran- spiration per hour by the rate of conduction per hr. The factor thus obtaind represents the amount of water that is transpired for every One centimeter of conduction. With the solution at a lower temperatur in one out of two simul- taneous sets but the evaporating ability of the air the same it takes – 50 - a smaller amount of transpiration to account for l cm of conduction. From this it does not appear that there need be a direct relation between the water actuańly lost and the conduction, just as there need not be between water intake and outgo as Preezer (1900), Renner (1911) and many others hav shown. It is known in work with herbs that a wilted or incipiently dry plant absorbs and conduct somore water in proportion to what it transpires than a turgid plant until the satura- tion deficit becomes alleviated. The bog shrubs do not show inci- pient drying by obvious wilting, altho no doubt it is present at times. The checking of the relativ rate of transpiration because of the ne— cessity of bringing the colder water up more degrees of temperatur, permits a relativly greater amount of the water absorbed being utilized in degreasing the saturation deficit, which existed when the plants Were collected. Utilizing the high temperatur of the steam radiator in the laborat- ory it was found that a much greater (2-4 times) amount of water loss occurred in proportion to the amount of conduction in plants kept in solutions at the radiator temperatur than near freezing. The high temperatur of the radiator (up to 53°) was above the death point of the plants and far above any temperatur that their roots are ever subjected to in natur. Plants maintaind in solutions near the freezing point in the extreme evaporating condition of the atmosfer above the radiator – a condition which is more severe, both with respect to summer heat and Summer soil water temperatur, than any ever experienced by Chamaedaphne in its natural habitat and for a long time – exhibited a higher transpiration and a higher rate of conduction than plants kept in the room at both room and freezing temperaturs. This was in spite of the Gold solution. A comparison of the transpiration-conduction factor With that of plants in cold solutions in the room shows scarcely arly difference. - 51 - With cuttings experimented upon outdoors it took even less transpiration for acgiven amount of conduction. The logical conclusion substanciated by these data is that the ability of plants of Chamaedaphne to conduct water is all times in natur, above -15°C, (the lowest temperatur at which experimentation was conducted) greater than the necessity and xerofytic modification in any part of the plant is not a result of the lack of ability to conduct, Water. The occurence of temperaturs of -159 is efrequent in the natural range of these plants and no injuries are apparent. At a temperatur lower than —25 such as occurd during February 1912, the drying up of the exposed leavs, twigs and flower buds of Chamaedaphne is first hand evidence that at such a low temperatur the conduction in the upper part of the plant is not sufficient to supply the transpiration demands. The Relation of Winter to the Xeroflytism of Peat Bog Ericads. Among peat bog plants, ericads with but few exceptions retain their leavs during the winter, when other plants are leafless. This is usually considerd as a matter of heredity. The presence of leavs very materially increases the evaporating surface of the plant and thereby enchants the amount of water to be absorbed. - That the different ericads experimented with differd among one another in their transpiration ability with their degree of protection from excessiv evaporation during the winter and that Chamaedaphne, the least protected, transpires considerably more than the leafless shrubs and trees indicates both the effectivness of the deciduous habit as a Xeroflytic ############ adaptation and the necessity of there being other xerotytle modifications in the case of the ericads. Added to this the difficulty of absorbing water, if for no other reason due to colder temperatur of the bog soil in winter and the necessity of xerofytic modification is apparent. The presence of so many of the usual xerofytic modifications in these peat bog ericads is noteworthy. The thick cuticle, dense palisade layer, more or less sunken stomates, hairs, scales, bloom and waxy coverings, restºn, upright position of the leavs are all indications of this xerofy ty, this necessity of keeping the transpiration within the limits of absorption and cond- ustion. From the experimental work it was evident that supplementing any water vapor absorbed by the leavs the rates of absorption and conduction in the evergreen ericads is more than ample to furihish sufficient water for transpiration auring warn spells in winter and for colder tempera- turs down to at least -15° for continued periods. When, however, continued temperaturs lower than -20° prevail in this region the rate of conduction is not sufficient to prevent drying and death of the ex- posed parts of the plant. On this point the winter of 1921–12 was remarkable evidence. Consequently, in view of the evergreen habit, which must be con- siderd as hereditary, a high degree of Xeromórfism is demanded to compensate for the lack of a decrease in leaf surface during the winter. - 55 - Experimental work during the Summer- Transpiration. The water loss of plants is greatest in amount during the summer as the growing season will be called for convenience in opposition to the winter. The greater evaporating power of the air, the greater ex- posur of most plants, the greater availability of water and the use of water in fotosynthesis all express the direct opposit of the conditions in winter and show the greater need for water in the summer. The purpose of the summer work was to obtain a knowledge of the transpiration of ericads, other shrubs, trees and herbs, growing under bog conditions and to make comparisons of the data. A part of the work was carried on at First Sister Lake and some of it at Mud Lake, but the bulk of the work was performa in the labora- tory upon plants that had been obtaind at First sister Lake. at the time of experimentation. Materials and Method. The same methods were employd that were used in the Winter work. Experimentation was extended over a much wider Variety of plant material which the summer season afforded. In addition to cuttings which were used in great abundance thruout the work a num- ber of bog plants were potted at First Sister Lake and allowd to remain in the bog until experimented upon a month later. They were brot into the laboratory in groups of six and the transpiration determined by Weighing at frequent intervals. To permit no water loss except from the plants the pots were incased in aluminum shells closed over with rubber dam and sealed with wax. Cuttings were run with each set of potted plants to determin the relation between them. An open dish of water Was run thruout the experiments to obtain an expression of the evapora- ting power of the air. At the close of each set the leaf surface was measured with the polar planimeter and the volume of the leavs determined by the amount - 54 - of alcohol displaced. The results were reduced to standard bases of grams per hour per 100 square centimeters of leaf surface and grams per hour per cubic centimeter of volume with the aid of a K & E slide rule. Experiments of May 6–7, 1911 on transpiration outdoors of cuttings of Populus tremuloides, Larix laricina, Chamaedaphne calyculata, Andromeda glaucophylla and Vaccinium macrocarpum. Day period Night period 9.00 to 18. 50 18.50 to 8. 50k --------------------------------------------------------------------------- Populus tremuloides *::::: . 243 .085 g/hr/100 cm? Larix laricina 4,162. 3,416.2.4 (.561 . 189 g/hr ) -- - L X - - ******, *.*** ) . 629 .077 g/hr/100 cm.” Chamaedaphne (Cham. assoc.) 4164.7 416 4.8 , 420 • 125 Chamaedaphne (Carex assoc.) 4.165.9 4.165. 10 ... 645 .192 Andromeda glaucophylla 4166. 11. 4166 - 12 . 940 • 358 Vaccinium macrocarpum 41.67. 13 4167. 14 . 915 • 254 Temperatur. 15 to 32 14 to 6 to 31 OC These data indicate that ericads without exception transpire at a decidedly higher rate than does a non-bog tree under bog conditions. The day rate is much greater than the night rate. - 55 - Experiments of May 22–23, 1911 on transpiration outdoors of cuttings of Chamaedaphne galyculata, Andromeda glaucophylla, Aronia melanocarpa, Nemopanthes mucronata, Acer rubrum, Larix laricina, Gephalanthus oggidentalis. Night period Day period 16.00 to 4.75 4.75 to 17.00k ------------------------------------------------------------------------ Chamaedaphne (Cham. assoc.) 4.198. l 4.198.2 ,058 .317 g/hr/100 cm.” Andromeda (Cham. assoc.) - 4.199:#5 • 200 . 655 Aronia melanocarpa (Cham. assoc.) 4200. 4, 4200 - 5 .062 . 715 Nemopanthes (Cham. assoc.)4.201.6 .021. - 15 l Acer rubrum (Larix assoc.) 4202.7 ... O 33 .214 Larix (Larix assoc.) 4203.8 - 0.53 . 161 Cephalanthus (Salix-Geph. assoc.) 4204.9 .067 .335 Temperatur 26 to 17. 5 18 to 32 to 239 - On the basis of the same evaporating conditions of the air the rate of transpiration of bog trees is lower per unit area than bog shrubs. That of northern bog shrubs is lower than that of southern Swamp Ones. Experiments of June 14-15, 1911 on transpiration outdoors at First Sister Lake of cuttings of Gephalanthus occidentalis, Aspidium thelypteris, Spiraea salicifolia, Ghamaedaphne calycu- lata and Ager rubrum set up in bog water. - 56 - Night period Day period 15. 67 to 6.50 6 - 67 to 12. 50k --------------------------------------------------------------------- Cephalanthus (Salix-Ceph. assoc.) #4240 .048 g/hr/100 cm” – Aspidium thel. (Iris assoc.) #4241 #4242 - 06 l - Spiraea (Cham. assoc.)#4243. ... 0.51 - - Chamaedaphne (Cham. assoc.):#4244 .044 . 280 Acer rubrum (Tree in Larix assoc.) #4247 .0ll ... O 31 Acer (seedling in Larix assoc.):#4245 .027 .092 Acer (seedling in Cham. assoc.)#4246 .051 ... O 99 Temperatur - 50 to 8 to 11 11 to 350 deW. The transpiration of a bog tree species is lower than that of the bog shrubs which in turn is lower than that of a bog herb, Aspidium. Experiments of June 15–16, 1911 on transpiration outdoors at First sister Lake of cuttings of Sagittaria latifolia, Aspidium thelypteris, Eupatorium perfoliatum, Chamaedaphne calyculata, Potentilla palustris, Larix larigina, Nymphaea advena, Ilex verti- eillata, Nemopanthes mucronata, Cephalanthus occidentālis, Aronia melanocarpa and Cornus paniculata, set up in bog water. A. M. period P. M. period Night period 10 - 28 12.95 19.67 to 12. 30 to 19.67 to 8. 37k Sagittaria (Iris assoc.) #4248 .294 g/hr/100 cm2 Aspidium (Iris assoc.) #4249 . 264 Eupatorium perfoliatum (Carex assoc.) #4250 . 241 Chamaedaphne (Cham. assoc.):#425l. .467 .277 - 0.49 - 57 - Potentilla palustris (Cham. assoc.) #4252 - 530 Larix (Larix assoc.) #4253 - 508 - 206 Nymphaea (Cast–Nym. assoc.)#4254 .670 (much wilted) Ilex (Cham. assoc.):#4257. ... O 91 Nemopanthes (Gham. assoc. #4258 ... 105 .017 Cephalanthus (Carex assoc.):#4259 . 206 (wilted) Cephalanthus (Salix-Ceph. assoc.)#4260 .293 (not visibly wilted. ) Aronia (Cham. assoc.):#4261. . 360 Cornus panic. (Cham. assoc.) #4262. ... O 90 When cut in the morning after the sun is well up the more typical hydrofytes wilt very rapidly and the stomates close and further cut down the water loss. This explains the apparently low rate of Sagitta- ria, Aspidium and Eupatorium which as a rule transpire at a greater rate than Chamaedaphne. Experiments of June 16–17, 1911 on the transpiration outdoors at First Sister Lake of cuttings of Chamaedaphne calyculata, Andromeda glaucophylla, and Vaccinium macrocarpum, set up in bog water. - 58 - 8. 52 to 10 - 58 10. 58 to 12. 57 14. 72 16.60 19.55 K. to 19. 55 --------------------------------------------------------------------- Chamaedaphne #4263 (Cham. assoc) 4264 4.265 Andromeda #4266 (Cham. assoc) 4267 Vac. macroc. #4268 (Cham. assoc) 4269 Chamaedaphne #4270 (Carex assoc)4271 Temperatur Relativ humidity Weather 1. 210 1. 139 . 571 24.79 57% pt. Cy .782 ... 611 • 354. 25 62 C . 6 22 • 465 - 298 25 68 l o u d y . 415 • 349 . 171 21 75 . 27.4 ... 255 ... 105 18 84 ... O 29 15 90 to 100% mist. The early morning promised a hot day. The temperatur rose rapidly and the relativ humidity dropt until about 10. When the sky became cloudy, the temperatur began to drop and the relativ humidity to rise. These changes found expression in the drop in the rate of transpiration which changed the character of the curv from that ºf a "normal" day, evidence that transpiration depends on the evaporating power of the air. - 59 - Experiments of May 6–7, 1912 on the transpiration in the laboratory of cuttings of Aronia melanocarpa, Chamaedaphne cally gu- lata, Larix laricina and Acer rubrum set up in distilled Water. Yºoung shoots were present on the deciduous species. ----------------------------- Aronia (Cham. assoc.) #4752. .9eo .588 .247 . 144 g/hr/100 cm.” Chamaedaphne (Cham. assoc.) #4753, 4754. • 441 - 545 • 210 . 215 ºf Aronia (Cham. assoc.) #4752. . 266 . 163 .06.8 .040 g/hr/cc Chamaedaphne (Cham. assoc.) #4753 4754 • 240 - 190 - 119 - 123 # Larix (Larix assoc.) #4755 4756 - 243 - 199 - 226 - 192 #f Acer rubrum (Larix assoc.) - #4757 4758 • 113 - 113 - 080 . 069 # Dish of Water. 1.175 1.209 .982 .881 g/hr/100 cm.” itemperatur 269 27 26 - 5 25 Relativ humidity 41% 44 ° 45 47 % --- Altho the evaporating power of the air, as measured by a free water surface was greater in the afternoon than in the morning all the cutting showd a decrease in transpiration, whereas the temperatur and relativ humidity were nearly constant. This was least noticed in Acer in Which the stomates seem never to close than in Aronia in which the Stomates close. – 60 - ExperiHatants of June 4–6, 1912 on the transpiration in the laboratory of cuttings of Chamaedaphne calyculata set up in bog Water and in distilled Water. June 4 June 5 - Jun 6 15. 68k to 22. 55 6.65 11. 55 17. 18 8. 40k ------------- Chamaedaphne #4770 - (Cham. assoc.)4771 , 105 .080 .074 .087 .070 g/hr/100 cm? 4772 d i s tº i l l e d w a t e r Chamaedaphne #4775 (Cham. assoc.) 4774 - 103 - 084 - 08.4 .098 - 084 4775 Dish of water .792 - 6 44 . 676 - - 532 Temperatur 22° 20 20 22 20 Relativ humidity % 51 51 52 6 L - 1he greater difficulty of transpiring from bog water as against distilled water is here shown and may be exprest as a ratio 100 to 109. Experiments of June 18–19, 1912 on the transpiration in the laboratory of cuttings of Aronia melanocarpa, Spiraea salicifolia, Chamaedaphne calyculata, Gaylussagia baccata and Salix pedigella- ris set up in distilled water. - 9. 47 to 14, 55 17.05 21 - 10 7.87k ------------------------------------------------------------- Aronia (Cham. assoc.) #4776 4777 . 52 • 28 • 26 .22 g/hr/100 cm.” Spiraea (Cham. assoc.) #4778 4779 . 16 . 17 - 17-- - 15 Uhamaedaphne (Cham. assoc.) #4780 4781 ... 10 ... 10- .09– .08 Gaylussacia (Cham. assoc.) #4782 47.9% .09 . O'7 • O6 - 06 Salix(Iris assoc. , 4785 ... 61 • 60 • 60 . 55 Dish of Water • 59 . 57 ... 6.7 • 50 leſſperatur 20 O 20 20 19 Relativ humidity 57% 57 58 66% ---------- – 6 l - This experimentation shows the nearly uniform rate of transpiration under nearly uniform conditions. The ericads, as usual, showing a lower rate than the other shrubs. That certain plants hav the ability per unit area to lose more waterAthan a free water surface is exhibited in the results upon Salix pedicellaris. Experiments of June 24–25, 1912 on the transpiration of cuttings of Chamaedaphne galyculata, Nemopanthes mucronata, Cephalanthus occidentalis and Potentilla palustris set up in distilled Water - in the laboratory. 15. 50k 21. 50k to 21 s 50 to 7 - 60k Chamaedaphne (Cham. assoc.) #4784 .08 .07 g/hr/100 cm? Nemopanthes (Cham. assoc.) #4785 . O'7 - 06 Gephalanthus (Salix-Ceph. assoc.) #4786 • 19 • 23 Potentilla pal. (Iris assoc.) - #4787 . 58 . 45 Dish of water . 74 . 57 Temperatur 240 22 Relativ humidity 50% 60 % ihese cuttings were made in the heat of a hot day at the time of severest transpiration and brot into the laboratory. With the exception of Chamaedaphne all were obviously Wilted more or less severely . The stomates were closed on all. This explains the very low rates of transpiration obtaind in these experiments. Even under these conditions Gephalanthus exhibits a decidedly higher rate than the northern bog shrubs, while the herbaceous plant showd a still higher rate. - 62 - Experiments of June 30–July 1, 1912 upon the transpiration potted plants of ########xof Carex filiformis (Carex association), Potentilla palustris (Carex association), Vaccinium macrocarpum (Chamae- daphne association), Aspidium thelypteris (Iris association), ghaſuaedaphne calyculata (Chamaedaphne association), Andromeda glaucophylla (Chamaedaphne association) and upon cuttings of Potenſtilla palustris (Carex association), Vaccinium macro- garpum (Chamaedaphne association), Chamaedaphne calyculata (Chamaedaphne association), Larix laricina (Larix association), Andromeda glaucophylla (Chamaedaphne association) set up in distilled Water outdoors and upon cuttings of Carex filiformis (Carex association) and Andromeda glaucophylla (Chamaedaphne association) set up in distilled water in the laboratory. From this series of experiments, the data for which is found on the following page and is grafically represented in Plate \o , it appears that the rate of transpiration follows quite closely the evaporating power of the air but does not excede about 1/3 of its actual value per unit area. The ericads in general transpire at a lower rate than the herbaceous plants. This is especially true of Chamaedaphne in which the rate of transpiration is 1/4 to 1/2 that of the herbaceous plants used. A comparison of the graf's of transpiration determined by cuttings and potted plants indicates that under the conditions of this day the curvs are similar. The cuttings of Vaccinium and Andromeda in this experiment transpired at a higher rate While one of Ghamaedaphne transpired at a lower rate than the corresponding potted plants. A cutting of Potentilla palustris, altho transpiring at but 2/3 of the rate of the potted plant was so wilted at the end of 3 hours that it Was taken down. 8.08k Jun 30. to tºll. 5l 16.00 20. 30 ------------------------------------------------------------------------- g/hr/100 cm? P o t t e d P. l a n tº s. July 1, 1912 6.90 8. 98 O. 23 O. 91 O. 54. 1 . 57 O. 27 O. 86 O - 45 0.92 o.13 O. 27 O = 32 l. 27 11. 10 15. 32 1. 47 l. 79 2. 42 2.88 1. 48 1. 55 1.65 2.0% O. 57 0. 6.8 2, 22 2.65 1. 87 2.90 l. 61 2. 24 O.7% 2.63 1.64 6.89 8.55 11. 52 10.95 16 24. 25 29 200 ---------------------------------------------------- 0.35 0.06 0.33 g/hr/100 cm? 0.05 g/hr/cc. O. 10 0. 51. O - 86 210 Carex filiformis #4788. 1. 26 1.86 O. 55 Potentilla palustris #4789 2.05 2.56 l. 17 vaccinium macrocarpum #4790 l. 15 1.38 0.44 Aspidium thelypteris #47.91 1. 26 1.70 (). 89 uhamaedaphne calyculata#4792 0.50 0.63 0.17 Andromeda glaucophylla #4793 l. 46 1.67 0.56 Dish of Water 6. 10 10. 51 5. 52 Temperatur 230 25 15 10 Relativ humidity 52% 40 €2 C u t t i n g s . Potentille palustris #4794 l.23 - - Vaccinium macrocappum #4795 l.29 l. 49 0.64 chamaedaphne calyculata#4796 0.27 0.44 0.11 Andromeda glaucophylla #4798 l. 53 l. 59 0.75 Larix laricina #4797 0.39 O. 41 0.10 C u t t i n g s i n t h e 1 a b o r Carex filiformis #4799 0. 54 (). 43 0 - 21. Andromeda glaucophylla #4800 l.06 0.96 0.71 Dish of Water 1.01 l.06 1. 15 Temperatur 24.5° 25, 5 22.5 Relativ Humidity 56% 48 50 60 % - 64 - Experiments of July 1–5, 1912 upon the transpiration of potted plants of Chamaedaphne calyculata (Chamaedaphne associ- ation), Eupatorium perfoliatum (Iris association), Dulichium arundinaceum (garex association), Andromeda glaucophylla (Cha- maedaphne association), Sagittaria latifolia (Iris association) and Asclepias incarnata (Carex association) and upon cuttings of Eupatorium perfoliatum (garex association), Dulichium arundinaceum (garex association), Asclepias incarnata (Carex association), Sagittaria latifolia (Carex association) and Chamaedaphne calyculata (Chamaedaphne association) set up in distilled water and all run out doors in the sun. (The data will be found on the following page. ) Experiments of July 4–6, 1912 upon the transpiration of potted plants of Carex filiformis (Carex association), Aspidium the lypteris (Iris association), Chamaedaphne galyculata (Chamaedaphne association), Acer rubrum (Carex association) and Sagittaria latifolia (Iris association) and upon cuttings of Hyperioun virginicum (9arex association), Acer rubrum (Carex and Chamaedaphne associations), Gaylussacia baggata (Chamaedaphne association), Cicut a maculata (Chamaedaphne association), Nemopanthes mucronata (Chamaedaphne association) and Typha latifolia (Phragmites-Typha association) set up in distilled Water and run outdoors. (The data will be found immediately succeding that of the above experiments. ) – 6.5 - July 2, 1912 July 3 20. 15 to 6. 20 9. 17 10. 95 15. 55 15.90 19 - 25 21, 37 5. € 3 P o t t e d Jº P 1 a n tº s . g/hr/100 cm.” Chamaedaphne calyculata 0.04 0.25 0.39 0.61 0. 37 0.30 0.05 +0.03 #4802. Eupatorium perfoliatum #4805. 0.18 0.79 1.06 1. 60 0.86 0 , 52 0. 16 0.05 Dulichium arundinaceum - - #4804. O. 17 O. 65 0.96 1.50 O. 94 0.56 O. 18 0.05 Andromeda glaucophylla #4805. 0.15 0.44 0.87 l. 28 0.49 0. 60 0.23 0.0l Sagittaria latifolia #4806. O - 26 O. 95 1. 65 2.26 1. 39 0.80 0 - 22 O. 13 Asclepias incarnata - #4807. 0.09 0. 60 0.90 1.56 0.79 0.54 O. 12 0.04 Dish of Water 1. 85 4.82 6 - 6 3 1C). Ol rain 3. 16 O. 97 0 . 19 Temperatur 12O10 15 29 3C 54 52. 20 25 21 18 20 Relativ Humidity 59% 75 57 58 47 100 74. 91 95 ----------------------------------------------------------- C u t t i n g s . Eupatorium perfoliatum - - #4808. 4812 0. 51 0 , 55 0.45 0 , 51 0 , 26 0.24 0 - 15 0.04 Dulichium arundinaceum #4809. 4815 0.29 O - 6 4 0 , 53 O - 49 Asclepias incarnata #4810. - 0. 57 O. 59 1.05 - 0.46 O. 42 0. 13 0.05 Sagittaria latifolia. #48ll. 4814 (). 28 O - 81 0 - 88 0.80 Chamaedaphne calyculata #4813. 0.05 (), 22 O - 41 0. 96 0 - 15 O - 15 O = 0.5 0 < Ol Tiz "O iyi, "O *O "T 9T * 3 39 "O GT * T 33 * T GS 02 03 * Z. T2 " I tº 9°3 62 * T 67 "T 4.9 "T 2g "O 6? 63 GA," TT g/, "T 92 °2 tº 9°. T g3 * T *G 36 °6 69" I 23 ° 93 24, "T 69 "T in 6 "I 09 "O 89 02 O2 * 9 *I*T 20° 3 2T *T 2T * T 93 * T 28 33 90° 3 92 * 0 99 "O --------------------------------------------------------------- 30" ZT – 6 6 - 8. O8 to 10.58 15. 35 1 P o t t e d P 1 a n tº s . Carex filiformis #4818 2.18 Aspidium thelypteris #4819 1. 26 Chamaedaphne calyculata #4820 1.33 Acer rubrum #4821 O. 97 Sagittaria latifolia #4822 2.95 Dish of Water July 4, 1912 2.60 1.25 1. 24. 1.02 3.07 10. 20 10 - 21 Temperatur 51937 35 Relativ Humidity 55% 45 5. 32 16.85 ------------------------------------------------------------------------ 2.30 1.06 O. 85 0.95 2. 15 7. 69 35 48 2. 33 1,02 O. 90 O. 95 1.98 7. 21 32 52 0.94 O. 56 0. 44 0. 51 O. 90 4.04 28 59 0. 56 O. 32 0.29 O. 16 0 - 31 O. 13 0, 16 0 - 16 0.08 0.29 ---------------------------------------------------- C u t t i n g s . Hypericum virginicum #4823.4824 l. 37 Acer fºubrum #4825 4827 O . 90 Gaylussacia baccata #4826 l.05 Uhamaedaphne calyculata #4828 0.63 Cicuta maculata #4829 1.51 Nemopanthes mucronata #4830 1, 52 Typha latifolia #4831 O. 70 1 s 60 0 - 6 2 0 - 80 0. 54. 1 - 0.2 1. 44 0. 55 0.79 O. 59 0. 55 0.28 0.79 1. 16 0. 54. 0. 51 --> C - 16 0.25 O. O'7 O = O 5 O. O 5 (nearly wilted) 1 - 17 O - 24 O ... O 5 (wilting thruout ) 0.14 0.04. O. l.0 O ... O 5 0.05 – 66a - July 5, 1912 Jy 6. 9. 10 11.05 15. 23 15.07 16 - 55 19. 57 20. 90 6 . 90 0. 53 l. 42 2.41 3.99 1.01 0 - 6 4 0 - 21 0.15 O - 45 0.90 l. 26 1.56 0.98 O. 43 0 - 26 O. 16 O - 42 1.01 l.09 1.70 O. 85 O. 27 0.22 C - 12 0.25 0.78 l. 10 l, 55 0.92 0.40 O. 10 O. O7 0.78 2. lº 5. 28 4.82 2. 34. O. 65 O. 35 O. 32 - 5.04 12. 35 14. 42 6 - 22 2.89 2. 33 1.02 26 - 5 29. 5 55 43 52 50 26 25 25 76% 59 45 4l 55 67 67 78 During the first week of July 1912 the transpiration of three series of potted plants was determined at frequent intervals. As this week was one of extreme hot, dry weather it will well serve to indicate the limits of transpiration to which these plants may be subjected to in summer. At the beginning of each series of potted plants a number of cuttings were also run to enable a comparison between cuttings and potted plants of the same species. With the potted plants it is noteworthy that with but a single exception the period of maximum transpiration is reacht at the time of maximum evaporating power of the air which ordinarily occurs in this region a little befor the middle of the afternoon. The graf's of evaporating power of the air and those of transpiration of the potted plants accord quite closely. Per unit area, however, between three and five times as much water is evaporated from a free water surface as from leaf surface. With cuttings somewhat different results were obtaind. Altho exceptions were not infrequent, in general the maximum daily transpirat- ion rate was reacht befor noon. This is two to four hours befor that of the maximum evaporating power of the air. Éxceptions ocurd on the less extreme days and were more general in shrubs. In this respect, Chamae- daphne especially is worthy of consideration. The maximum rate of transpiration of cuttings of this plant took place at the time of maxi- mum evaporating power of the air except on one day (July 4) when the cuttings were made in the morning. A comparison of the results of potted plants and cuttings of the same species, altho exhibiting more or less variation, in general, shows that the rate of transpiration is greater in the potted plant. The difference is usually greatest at the time of maximum evaporating power of the air. Under less extreme conditions of evaporation the grafshf transpiration of cuttings accord more closely with those of – 68 - potted plants than when under extreme conditions. From this it follows that one can obtain a knowledge of relativ values under moderate conditions by means of cuttings but experimentation at extreme conditions of evaporating power of the air is unsatisfactory. This may in part explain the results of Lloyd (1908) on Ocotillo (Fouquieria splendens) in which he found that the maximum transpira- tion rate determined with cuttings occurd befor the maximum evaporating power of the air obtaind. Inspection of the data shows that the rate of transpiration is notably lower in the ericads, especially Chamaedaphne than in other shrubs and in the herbaceous plants. The bog tree, Acer rubrum, how- ever, transpired at a lower rate than does Chamaedaphne. Experiments of July 8–9, 1912 on the transpiration of cuttings of Picea Inariana, Larig laricina, Chamaedaphne calyculata and Vaccinium corymbosum obtaind from Mud Lake and set up in distilled water in the laboratory Cupelo. – 69 – July 8, 1912 Jüly 9. 7.88 to 15, 12 19. 38 7. 58 k T. . . . . . . . .T 27.71567.3T. Chamaedaphne calyculata #4895 O. 65 O. 52 0 - 11 Vaccinium corymbosum #4896 l. 14 O - 89 0 - 17 g/hr/ce Picea mariana #4893 O. 17 (). 16 0.04 Larix laricina #4894 0.48 O. l? O. 10 Chamaedaphne calyculata #4895 0 - 31 0.26 0.05 Vaccinium corymbosum #4896 0. 58 0.45 0.08 Dish of water 8.75 6. 32 1. 52 Temperatur 27O 53 26 520 Relativ Humidity 68%. 42 71. 58 7. bog These results indicate that a deciduous Atree and shrub make a larger demand upon the water supply per unit volume than do an ever- green tree and shrub. The evergreen tree, spruce, makes a lower demand for Water than Chamaedaphne and the latter is less exposed. Experiments upon the rate of Conduction by the Lithium nitrate Method during the summer- The determination of the rate of conduction which actually takes place can only be approximated by the lithium nitrate method as potted plants are not available in which one can know at just what time the lithium nitrate enters the root system. Accordingly cuttings were used thruout . As it was desired to obtain the relativ rates of several plants under the same conditions rather than the highest values which could be obtaind under varying conditions, the following precedur was adopted. The cuttings were obtaind in the early evening when the stomates were closed, cut under water, brot into the laborato- ry, again cut under water and allowd to remain under laboratory con- ditions over night where the sun could strike them in the early morning. The following morning the stems were cut off under lithium nitrate solution in shallow dishes and allowd to remain for a certain period. At the expiration of the period the stem was removed from the solution very quickly cut up into pieces one centimeter long and later tested in the spectroscope. Experiments of July 6 1912 on the conduction of certain stems under laboratory conditions (temperatur 319, relativ humidity 61 to 56 % ). Duration of experiment one hour. No. of stems tested Cond. in cm/hr ---------------------------------------------------------------------- 5 Andromeda glaucophylla. 5 21 Maccinium macrocarpum 5 Larix laricina 5 more than 31 cm, the length of the Cephalanthus occidentalis 5 º tº 27 longest stem. Aspidium thelypteris 5 if * 30 ºf Nemopanthes mucronata 5 #1 * 40 º Aronia Imelanocarpa 5 ff * 51 ſt Salix pedicellaris 5 ºf " 35 t - 71 - Experiments of July 6, 1912 on the conduction of certain stems for 15 minutes under laboratory conditions of 33° and 48 %. INo. of stems tested Conduction --------------------------------------------------------------------- Chamaedaphne calyculata 2 - 19.7 cm/hr Spiraea salicifolia 2 48.0 Acer rubrum 2 70. O Cephalanthus occidentalis 2 more than 140. Experiments of July 8, 1912 on the conduction of certain stems for 15 minutes under laboratory conditions of 250 and 69 % R.H. --------------------------------------------- Larix laricina 2 47 cm/hr Picea mariana 2 26 Vaccinium corymbosum 2 6O Chamaedaphne calyculata 2 13 Nemopanthes mucronata 2 21 Experiments of July 9, 1912 on the conduction of certain stems for 10 minutes under laboratory conditions of 269 and 69 % R.H. Asclepias incarnata 2 210 cm/hr Eupatorium perfoliatum 2 84 Sagittaria latifolia (wilted) 1 49 Chamaedaphne Calyculata 3 22 Hypericum virgin; Gunſturgid) l 76 ºf (just beginning to wilt) 1 126 Potentilla palustris 2 86 Typha latifolia 2 ll. x ºf of C O º º - . - - | 7 || . n the greenhouse. - - Ch *: º 32-2-2-3 - - 0 tex -v-bew ºf $11-18. -- : Y \ewwo aw Wels ww.crowavº ºstº. -º-º-º-º- º | a \ \x \ovºcrats *4310-3 | --~~~~~ : 50 WX feate-\º * + 3 al-26. - - |00 º, Rºº º º - º - +3°S - ^ * Tºwn º, - Peº-º-º: \ \ \ }- f / O | | /2 (?, lood 3/8-ſco exº~~~ ck..…yº Sº #2 cº-5- X. alsº a vovº e cºo- - += #3 o 2-3 Val-cºva wº nº cº-c . * ºf 3 c 3 - | F 6, 6 º'o C º “ º - * is sºlº ſºlº ſºlº ſºlº - Graf's obtaind from the outdoor. experimentation upon potted plants. Transpiration. Plate 15. ºf 4-2 a cy */ /7/2 // /3 Z5T (7 /7 // /3 A5 /7 /7 // /3 /5T (7 /7 2. OO - - - - º- Selwt to ºv R → own lan - Solºvt. ºr ºv § - e. º So lºt ºn R. Late -7. - 9//* 2. O’C. f o, 5 * 3, 1 3 T-4 Tº P 47°C /3 2 /60 35°C. - - * *438% ... "??? **333 º, *387 - 3 lºc ſo *:::: - 335- - A5 35 *4382. #3 &2. Recº Cºlºuras R.a. ten- ºactiºns | C). ºf R4. Hº, - - - . . . tº ºr Graf's of transpiration obtaind while experimenting upon the relation of solution and air temperatur to transpiration. | - | - - | Plate lºº. WA a voº, alo º 3. H 25 (2 7 3. - C. *º, * Cº- - | lavix \avic wo, (£2a4-33) of 5 O ºv ºrd ºvºvº º/*/ # #4%0. - - - - - - - - - Beto V. Fºº- (\cºſ less) sł- Hººft/. o 16 O o 0.5-0 | 2" N co O x. - O *† 42% 0°C. Tº - ºr - - - | - | Graf's of the results of transpiration of twigs in Winter outdoors. Plate 15. 3. 13. 14 zo 2% % 3. ...~~~~~ * %ver- \. gº/at - - - - sdo. Girarvia- |\\ ... lºss. Sº º – __N; - - ----- T*~~~ == - - , -o-º-n X- - # 73-37-374- -- - - - - := a --~~~} hr- * > *s-3-4 a ce-Yº -- - - - - - - - - - - - - - - - * 73-7-378 T - - - - -, Cac - vº 0-v-u-a º ºs-2 0. | - - - - T. - Fig. l. Graf's of transpiration in leafy twigs in early spring. 44 2O 2} % 3. * Za. -2O 2× % & . - I ./OO 20% 0.5°C ſo º ** ºloº Ó. Fig. 2. Graf's showing the relation of transpiration from bog water and from distilled water. Plate 16. - Craf's showing the relation of transpiration in cuttings and potted plants to the evaporating power of the air. | 2:00. * Jºe 30, 1412. 15 ſo a 1% /4. - /3 | | -- __ - - - - --~~~~ - 8. **** va-vºwa * ovoe»” º Toſſ. A pºss a v-e- *\o Velº- G * s vº. ºuvre. º º, *** c. v v^. C. v \o Cº. /2. | Plate 17. - (e) on the left, showing graſs of the relation of transpiration ef cuttings and potted plants to the evaporating power of the air. 15, od ſ/4/re ºv” (b) on the right showing graf's - of the transpiration of potted plants on an extremely hot day. | - - . - || -- N - W - | § 3. | º º * - - - 2 | º P 3. - º 7. º º - r º º - - (, . - - - ºvº. 5 r 2. - - Q - T',\\z\ \ºat, - º - al- > 8 : averº Foº º *\\ c & T. r Potte.A. \axºs & re- r *\ove vºv \SValcº . r r º ave *\º T wº ºl. 2 -- Plate is. J.A. 3-1112- Q & A 1 - 2– 3. / O /2. 7% /42 /? 2d 22 2% 2 */ 2 3. /, 0.0 *L*… Li- */ 0. 50 Ó foo . . - e J. - - G -- evº o-º-º-º- o --- ºr sea 2. cº-º- Lºº lo - - Graf's showing the relation of the transpiration of deciduous and evergreen conifers and ericads. - | | Plate 19. Diagram showing the successions exhibited by the bog plant associations in the vicinity of Ann Arbor, Michigan. Potamogeton Assoc. ! Castalia – Nymphaea Assoc. / Phragmites-Typha Assoc. Eleocharis Assoc. Carex filiformis Assoc. ! Iris Assoc. | Chamaedaphne Assoc. | Aronia-Vaccinium Assoc. I Salix-Gephalanthus Assoc. Populus Association. Larix Association. Ulmus-Acer Assoc (a non-bog associ- ation. ) RULES COVERING USE OF MANUSCRIPT THESEs IN THE UNIVERSITY OF MICHIGAN LIBRARY AND THE GRADUATE SCHOOL OFFICE Unpublished theses submitted for the doctor's degrees and deposited in the University of Michigan Library and in the Office of the Graduate School are open for inspection, but are to be used only with due regard to the rights of the authors. For this reason it is necessary to require that a manuscript thesis be read within the Library or the Office of the Graduate School. If the thesis is borrowed by another Library, the same rules should be observed by it. Bibliographical refer- ences may be noted, but passages may be copied only with the permission of the authors, and proper credit must be given in subsequent written or published work. 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