EUNIVER% "%3AV&> I LIBRARY^ x^HlBRARY^ y^.- t-^ \& l&UVD-JO^ FOB^ jnv3-jo^ ^F-CAIIF(%, j\l ^ fivwiH^ 1 ^Anvsan- * I I clOS-ANCEl clOS-ANCEl 1 -OF-CAUK HFp UNIVER%. ^clOS-ANCEl^ {I ^1 QOKVSO^ ^/SUAM^ -UN1VER% ^IDS-ANCH^. S 5 1 IOS-AMCE &WXL .5ME-UHIVERS/A. DUPLTC - BULLETIN No. 124 OCTOBER 1916 GEORGIA EXPERIMENT STATION EXPERIMENT, GEORGIA The Two Groups of Varieties of the Hicora Pecan and Their Relation to Self-Sterility By H. P. STUCKEY The Bulletins of this Station are sent free to all "persons actu- ally engaged in farming who make request for same," and all newspapers in the State. Address R. J. H. DeLOACH, Director, Experiment, Ga. RURAL1ST PRESS, Inc.-3524 ORGANIZATION Board of Directors HOX. j. D. PRICE Commissioner of Agriculture, Ex-Officio President of Board, Atlanta, Ga. D. C. BARROW, C. & M. E., LL. D. Chancellor of the University of Georgia, Ex-Officio Member, Athens, Ga. ANDREW M. SOULE, B. S. A., Sc. D. President State College of Agriculture and Mechanic Arts, Athens, Ga. Designated by the Governor. FIRST DISTRICT R. C. NEELY Waynesboro SECOND DISTRICT J. W. ANDREWS Carnegie THIRD DISTRICT W. D. HAMMACK Coleman FOURTH DISTRICT J. H. MOBLEY Hamilton FIFTH DISTRICT JOHN T. DUNCAN Douglasville SIXTH DISTRICT J. J. FLYNT Griffin SEVENTH DISTRICT JOHN W. L. BROWN Cartersville EIGHTH DISTRICT B. W. HUNT Eatonton NINTH DISTRICT L. G. HARDMAN, M. D Commerce TENTH DISTRICT A. S. CHAMLEE : Bartow ELEVENTH DISTRICT WILLIAM HENDERSON Ocilla TWELFTH DISTRICT F. R. MANN Jacksonville Station Officers R. J. H. DELOACH Director H. P. STUCKEY Horticulturist J. C. TEMPLE Bacteriologist P. V. EWING Animal Husbandman C. A. WELLS Chemist B. B. BIGGINS Botanist and Plant Pathologist c. K. MCCLELLAND Agronomist F. H. SMITH Assistant Chemist The Two Groups of Varieties of the Hicora Pecan and their Relation to Self-Sterility H. P. STUCKEY Some form of sterility in plants as the cause of much poor bearing has occupied the attention of horticulturists since the publication of Darwin's work in 1862 on the various contrivances by which orchids are fertilized by insects. Since then, few horticultural plants of any consequence have escaped notice in these searching investigations and many results of economic importance have been accomplished. Beach (3), Bailey, (2), Waite (4) and Waugh (5) were among the first horticultural investi- gators in this country to do systematic work on sterility in horticultural plants. This has been constantly added to by many other workers in later years. As nut trees became of commercial importance, whether or not they are self-sterile became an important problem. However, little work so far has been done along this line. Lewis (10) states that Persian walnut trees from four to six years old often start a heavy crop of nuts only to have them drop before maturity. "This," he says, "is due to the fact that young walnut trees do not produce sufficient catkins and therefore do not have a sufficient quantity of pollen. After the trees become older there seems to be less trouble from this source. With the young Froquette trees, it is especially noticeable that the catkins are scarce the first few years, but by the time the trees reach the period of heavy bearing, at seven years, there are generally sufficient catkins to insure a good crop. With the Magette, the female blossoms sometimes appear before the male, while with the Gladys, they are both apt to appear together." Itamsey (8) working with other varieties of Persian walnuts finds simi- lar conditions. No work has been done on self-sterility in pecans, the only record found is that by Berckmans (9) who states that sometimes staminate flowers of pecans appear before the pistillate flowers, causing poor crops of nuts. However, he gives no data on the subject. In the past eight years during which we have been working with the pecan, reports and inquiries have come to us from various sections of this state and from other states in regard to single trees or isolated groups of trees of a single variety that were shy bearers or that did not bear at all. This raised the question of whether or not some varieties of pecans were not partially or wholly- self-sterile. 233133 128 GEORGIA EXPERIMENT STATION Twig on left from Group I. Twig on right from Group II. Note how the Catkins of Group I protrude while the buds are still small. Two GROUPS OF THE HICORA PECAN 129 The Two Groups of Hicora Pecan and Their Distinguishing Characters In our work with the Hicora' Pecan, we found that the varieties easily fall into two distinct groups (1) which bear a close relation to the problem of self-sterility. These two groups are easily distinguished from each other by the floral characters of the catkins of staminate flowers ; and also, by the difference in development of the pollen grains of the two groups. In Group I, the embryonic catkins of staminate flowers are enclosed in rather short, broad, bud scales, one on each side of the leaf bud. The catkins themselves are rather short and broad as compared with their length, and the individual flowers of the catkins are shielded by short, rather small and inconspicuous bracts. The catkins of Group I protrude from one to five days before those of Group II protrude, and shed their pollen from five to ten days before those of Group II. With most of the varieties of this group, the pistillate flowers become receptive at about the same time that the staminate flowers shed their pollen. However, a few varieties of this group have a considerable percentage of their pistillate flowers to become receptive after the maximum dehiscence of pollen. In Group II, the embryonic catkins of staminate flowers are enclosed in long and rather slender bud scales. These catkins are usually narrower and longer than those of Group I and the individual flowers are shielded by long, narrow, conspicuous bracts. ' (Fig. 2.) In this group, the pistil- late flowers beqome receptive from two to ten days before the staminate flowers shed their pollen ; and, in most cases, a large percentage of the stigmas of the pistillate flowers have become dried or calloused before the pollen is she*!. The differences and some of the characteristics of the two groups is shown in the following tables, which gives some of the varieties grown on the Station grounds in 1915 and 1916: 130 GEORGIA EXPERIMENT STATION Two GROUPS OF THE HICORA PECAN 131 TABLE No. I GROUP I Variety Alley Date stigmas, receptive 5/1 5/1 Centennial Mobile Mantura Nelson Pabst . 4/30 5/1 5/1 4/30 4/30 Randal 5/1 Rome 4/30 Jerome 4/30 Robson San Saba 4/30 4/30 Date first pollen shed 5/1 5/1 5/1 5/1 4/30 4/28 5/1 5/1 4/30 5/1 5/1 5/2 Percent pollen germination GROUP II Variety Appomattox . . Atlanta Bradley Curtis Frotscher .... Moneymaker . Pan American President Russell Stuart Teche Van Deman . . Younjr Date stigmas receptive 4/30 5/1 4/30 4/30 4/30 4/30 4/30 4/30 4/30 4/30 4/30 4/30 4/30 Date first pollen shed 5/5 5/10 4/9 5/13 5/10 5/6 5/9 5/9 5/6 5/6 5/8 5/9 5/9 Date Percent stigmas dried pollen germination 5/5 15 5/5 40 5/5 35 5/7 40 5/6 40 5/3 20 5/5 40 5/5 15 5/5 5/5 20 5/5 50 5/5 .5 5/5 15 Phonological Data for 1916 In 1916 an effort was made to get more complete phenological data from the Station orchard as well as from a number of varieties of pecans grown in commercial orchards in the southern part of the state. To eliminate, so far as practicable, individual variations, more than one tree, of most varieties, were used in the 1916 records. In the following tables both groups of varieties are given, but the group number of each is indicated by numbers 1 or 2. instead of the groups being made into separate tables. 132 GEORGIA EXPERIMENT STATION jo q;3o9i noijuuitniaS nauod -jns ura3ps uanod paqs : SJBdddB S man EH JB31 3JBQ r^ r-i O i ^ CO ^^^^^^> ^^>^^^^^^ ^^^ OOXCOCOCO^OCOCC ^ICCt^b-^CCSOCC COSO^COCO^J 1 t- t o t- 1^ t- t- ir:i--t-siO tt ir: t- t- t-- L~ x t- Sh a) | ai(:tflS ^ o;=l '-' ctio l oc>&poo *S|-S-S'3os> K oa)fl t- oc" Si-Tcf pf'sTw'ctf b-^od e T-T cf cc" -^ L'f cc* b-^ 06" gi "c^f co"-^ kc'cc't-'cc' gi-Tw" co -^Lt" cc t-^od" GEORGIA EXPERIMKNT STATION stiiiuiiiute and pistillate flowers from a Pan-American tree. The stigmas hav dried and nut growth started, while no pollen has been shed from the Catkins. Two GROUPS OF THE HICOEA PECAN 135 In Group I of the 1915 table, it will be observed that the pollen shed at about the same time the pistillate flowers became receptive. This is very important in its bearing upon the question of whether or not those varieties are self-sterile. In Group II of the 1915 table, it will be noticed that the interval between the receptive stage of the stigmas and the first shedding of the pollen is much greater in this group than in Group I. In fact it was observed that one Moneymaker and one Van Deman tree had dried stigmas and young nuts had started into growth before the first pollen had shed off these two trees, respectively. Further, most of the stigmas of the different varieties of Group II had dried, showing that they were past the receptive stage, before the first pollen was shed. The percentage of pollen germination in Group I was very low in 1915. In making the germination tests of the pollen, only one trial was given each variety merely to determine whether the pollen was capable of germination. Further trials made under even slightly changed conditions, would probably have given different percentages of germination, for, as will be seen later, Group I gave in 1916 a much higher percentage of pollen germination, which was about equal to that of Group II of that year. In the 1916 table, it will be noticed that those varieties marked Group I shed their pollen at about the same time the pistillate flowers became re- ceptive as was observed in the 1915 table, while those varieties marked Group II, showed a like interval to Group II of the 1915 table, between the receptive stage of the pistillate flowers and the shedding of the pollen. The percentage of pollen germination in Group I of 1916 was about equal to that of Group II. Phonological Data from South Georgia for 1916 To determine the behavior of a number of varieties under different cli- matic and soil conditions we secured the co-operation of a few pecan grow- ers in the southern part of the state where the conditions are thought to be more favorable to pecan growing and where large commercial orchards have been planted. Below are given some data for 1916 on a large number of varieties, at Cairo, Ga., supplied us by Mr. J. Stater Wight, of that place : TABLE No. HI Variety Nelson Mantura Waukenah Alley Van Deman Schley Frotscher Teche Moore Curtis Delmas Mobile Lott No. 3 Success Pabst Lott No. 2 Moneymaker Stuart Oliver Centennial Georgia Giant Variety group 1 1 2 1 2 2 2 2 1 2 2 1 2 1 1 2 2 2 1 1 1 Date pistils receptive 4/14 4/15 4/20 4/22 4/24 4/26 4/24 4/24 4/21 4/26 4/26 4/25 4/28 4/28 4/29 5/2 4/24 5/2 4/29 5/1 4/28 Date first pollen shed 4/14 4/16 4/29 4/22 5/3 4/29 - 5/2 5/1 4/22 5/6 5/3 4/26 5/5 4/30 4/20 5/7 5/1 5/9 4/30 5/1 4/28 Days difference 1 130 GEORGIA EXPERIMENT STATION To determine the variation in time of blooming within the variety, Mr. Wight furnished the following data on Frotscher, Moneymaker, Wankenah, Teche and Stuart varieties: FROTSCHER WAUKENAH 5 trees shed first pollen April 2nd. 5 trees shed first pollen May 3rd. 76 trees shed first pollen April 3rd. 3 trees shed first pollen May 4th. 26 trees shed first pollen April 4th. TECHE 13 trees shed first pollen April 5th. 3 trees she d first pollen May 5th. 10 trees shed first pollen April 6th. 2 trees shed first pollen May 6th. 5 trees hsed first pollen April 7th. a tree shed flrst pollen May 7th. MONEYMAKER STUART 8 trees shed first pollen May 1st. a tree shed first pollen May 8th. 1 tree shed first pollen May 5th. 6 trees sned fi rst po llen May 9th. 1 tree shed first pollen May 10th. It will be observed that the difference in dates of blooming and the inter- val between the receptive stage of the pistillate flowers and the shedding of the pollen of the two groups of varieties grown at Cairo, in South Geor- gia, are very similar to these differences between the two groups of varieties grown at Experiment in north middle Georgia. The essential difference is that the varieties of both groups shed pollen, on the average, about ten days earlier at Cairo than at Experiment. This difference is very vari- able, ranging from one to fifteen days, which may be due to a difference in strain of varieties or the possibility of some varieties being misnamed at one or the other locations. Pecan pollen grains greatly enlarged from the Alley variety. Differences in Development of Pollen of the Two Groups In size, shape, and general characters, the pollen of the two groups of varieties of pecans differ almost none. But there is a difference, however, in the time or rapidity of the development of the pollen of the two groups. Two GROUPS OF THE HICORA PECAN 137 In general, pecan pollen is somewhat spherical and rather flattened in shape. It is rather large in comparison with pollen from other nuts, being of practically the same size as that of hickory, considerably larger than pollen of Japan walnuts, and larger still than that of the Spanish Chestnut. Pecan pollen grains have from three to five germ pores; and usually, in germinating, send out a tube through one pore. However, sometimes the pollen grains send out more than one tube. *The pollen mother cells, tetrads, and pollen grains form first, respectively, at the basal end of the catkins of stamina te flowers. Here, also, the pollen begins to shed first. The pollen formed at the distal end or apex of the catkins is often almost void of germ pores and not infrequently shows signs of degeneration in the nuclei. In the development of the pollen in Group I, the average difference in time between the tetrad stage and pollen formation was approximately two days, while for Group II the average was approximately two and one-half days. In Group I the average time between the pollen formation and the first shedding of pollen was approximately fifteen days, while that of Group II was eighteen days ; further these intervals vary less than do the intervals between the appearance of the catkins and the tetrad stages of the two groups. SMC Germinating pollen from the Nelson variety. * NOTE Normal pollen formation in pecans is the same as that in most other seed-producing plants. Within the embryonic anthers are formed pollen mother cells. Within each of those pollen mother cells four pollen grains are formed. The mother cell containing the four miscrospores or pollen grains is called a tetrad. 13* GEORGIA EXPERIMENT STATION A tetrad greatly enlarged from the Jerome variety. The following table gives the dates of tetrad aud pollen formation as well as the size of the pollen grains of several varieties being grown in the Experiment Station orchard. TABLE No. IV > o i 1 z a a a. o H O a t| fl) (4 <2 o ! 1 Q *i ii 11 Q 1 Q No. days from pollen form pollen shed Randal 4/13 1 4/17 4 48 5/1 14 \elson 4/11 1 4/13 2 48 4/29 16 Allen 4/13 1 4/14 1 48 5/1 17 Robson 4/14 1 4/17 3 44 5/1 14 San Saba Mobile 4/14 1 1 4/17 4/16 r> 44 48 5/2 5/3 15 17 Jerome Rome Centennial 4/14 4/13 4/13 1 1 1 4/16 4/14 4/14 O 1 1 48 48 48 5/1 5/1 5/2 15 17 18 Man t u ra 1 4/14 48 5/1 17 Beverage Triumph. 4/14 1 2 4/17 4/19 3 44 51 5/1 5/9 14 20 Pabst 1 4/17 48 5/3 16 Washington Schley 4/26 1 2 4/19 4/28 2 51 51 5/1 5/13 12 17 Van Deman 4/22 2 4/24 o 51 5/10 16 Stuart 4/21 o 4/22 1 48 5/11 19 Teche 4/21 2 4/22 1 51 5/13 21 Young Appomattox President 4/24 4/19 2 2 2 4/26 4/21 4/22 2 2 51 51 51 5/11 5/8 5/11 15 17 19 Atlanta 2 4/22 51 5/11 19 Russell 4/22 2 4/24 2 51 5/11 17 Frotscher 4/22 2 4/26 4 51 5/12 16 Curtis 4/22 r> 4/26 4 48 5/14 18 Pan American Hickory 4/22 2 1 4/26 4 51 55 5/12 16 Japan Walnut Snanlsh Chestnut.. 38 17x10 Two GROUPS OF THE HICORA PECAN 139 The Relation of the Two Groups to 'Self-Sterility The results of our work thus far leave little doubt that self-sterility in pecans is due primarily to the interval in time between the receptive stage of the pistillate flowers and the shedding of the pollen. Left to right Stigmas up 1. Nelson receptive; 2. Pabst just entering receptive stage; 3. Jerome just past receptive stage; 4. Frotscher receptive stage past, and stigma dried. Magnified 2% times natural size. Those varieties in Group I where the pistillate flowers are receptive at the time the pollen sheds, present no difficulties in the problem of self-steril- ity. But those varieties in Group II where the pistillate flowers are past the receptive stage, and the stigmas dried before the first pollen sheds are necessarily self-sterile in varying degrees according to the persentage of dried or calloused stigmas on the tree before the pollen begins to shed. These points were investigated by the usual methods of field observations, bagging, and crossing. In our field observations of Group I, as will be seen by referring to Tables 1, 2 and 3, all those varieties in Group I shed their first pollen at about the same time that the pistillate flowers become receptive, thus giv- ing ample opportunity, in most cases, for the pistillate flowers to be ferti- lized by pollen from the same tree. We found that the stigmas of the pistillate flowers remained in a fresh, undried condition for a period of several days, considerably longer than those in Group IT. However, all do not become receptive at the same time and we found that there is some danger of the varieties of Group I shedding their pollen too early for pol- linating all their own pistillate flowers, i. e. those coming into the receptive stage late. Observations showed that a number of stigmas of the Alley and the Randall varieties were still fresh and vicid after practically all the catkins of staminate flowers had dried and fallen. This indicates that it is possible, at least during some seasons, for the pollen of the two varieties to shed before all the pistillate flowers are fertilized. This is especially true if there should be heavy winds and rains at the time the majority of the anthers are dehiscing, for during such weather the pollen is either washed, or blown away. There is also some danger of the pollen, hanging in the old and dried catkins, not remaining viable for fertilizing the late pistillate flowers where such pollen is exposed to the weather conditions. To make a test of this point, on May 15, 1916, pollen was collected from the dried catkins hanging on the trees of the Alley, Jerome, and Nelson varieties and the usual germination test made. None of this pollen germinated even though the same varieties gave high germination tests about ten days previously when the pollen was taken directly from the dehiscing anthers. 140 GEORGIA EXPERIMENT STATION Branch from a Stuart tree showing: young Catkins intermingled with the larger ones. This gives a long period of pollen shed- ding. Unfortunately little of this is found among the early blooming varieties. In Group II by referring to Tables 1, 2 and 3, it will be noticed that the interval between the receptive stage of the stigmas and the first shedding of the pollen varied from four to nine or more days, thus making the pol- lination of the stigmas by pollen from the same tree rather difficult. How- ever, the difficulty in drawing definite conclusions from this lies in the fact that in making field observations it is very difficult to determine just when the stigmas of pecans become receptive and the exact time they pass the re- ceptive stage. Those stigmas of the pistillate flowers that were bagged and pollen excluded, dried or calloused at about the same time as those bagged and pollinated. In the further pursuance of the experiment an effort will be made to determine these points. To obviate this, however, we recorded the dates when the stigmas dried and calloused over sufficiently to leave no doubt that the receptive stage had been passed. From this, it will be seen that the varieties of Group II had their stigmas to dry and callous over from one to five days before the first pollen shed, thus practically pre- cluding the pollinating of the stigmas by pollen from the same tree. How- ever, in the case of the Curtis and the Stuart, a considerable number of belated pistillate flowers showed fresh stigmas on the date the first pollen was shed. In such cases when these varieties are grown alone, we would not expect complete sterility, but a light crop. Two GROUPS OF THE HICORA PECAN 141 An Alley tree showing bags in place. 142 GEORGIA EXPERIMENT STATION Sterility Avoided Through Mechanical Injury to Catkins It was observed that catkins of staruinate flowers broken off by the wind, or by other mechanical agencies, and left hanging in the trees where they became more or less dried, shed pollen several days before the normal dehisence of the anthers. To determine whether or not such pollen was viable, some catkins from a Curtis, and a Stuart tree, three and four days respectively before the first pollen was normally shed, were taken to the laboratory and allowed to dry at room temperature for twenty-four hours at which time the pollen had begun to shed. The usual germinatioH tests were made of this pollen with the result that 50 per cent of the Curtis and 62 per cent of the Stuart pollen germinated. While these catkins were pulled from the trees two and three days respectively before the first pollen shed, it is probable that they were pulled four or even five days before they would have shed their first pollen normally as the most forward catkins of the trees were probably not pulled. Such results make it possible that vari- eties of Group II could be partially fertilized from pollen of catkins receiv- ing some mechanical injury a few days before the pollen shed normally. Such trees, otherwise, might be wholly self-sterile. Parthenogenesis Indicated Pecans are like several other nuts in presenting many difficulties in bagging and cross pollinating. Morris (7) called attention to the development of seediugs grown from seedling Chinquapins, the flowers of which were bagged to prevent pollina- tion. "Subsequently check experiments indicate that the chinquapin will develop nuts freely without pollen ; and that the bitter nut hickory, shag bark hickory, and pig nut will develop nuts sparingly without pollen." Pistillate flowers of the pecan are terminal and appear on the current year's growth rather early in the season. At the time the bags are .to be put on there are a number of compound leaves somewhat shielding, and just posterior to the embryonic pistillate flowers that go into the bag readily at the time, but increase in size so rapidly that the bag is soon overcrowded. An attempt to remove these small leaves before bagging usually results in such injury to the young terminal that the pistillate flowers fail to develop. Again the young growth of the pecan is very sensitive to any abnormal con- ditions of air, light, or temperature, and is unable to withstand even very light mechanical injuries. The common yellow paper bags are almost fatal to the terminals if allowed to remain on very long. Cloth bags that are thin enough to allow the bagged terminals to grow under even approxi- mately normal conditions are liable to admit drifting pollen and thus make the results uncertain. Cloth bags sufficiently closely woven to keep out pollen are likely to injure the terminals to only a little less degree than paper bags. Therefore, the very thinest and lightest white cloth that will exclude pollen seems to be best for bagging the terminals. In 1915 we bagged 14 clusters of pistillate flowers on a ten-year-old Stuart tree, using thin, white and closely-woven lawn cloth for the bags. The fourteen clusters of pistillate flowers were treated as follows : (1) All catkins of staminate flowers removed and the cloth bag put on before the pistillate flowers became receptive. No pollen was applied to the stigmas and the bag was allowed to remain on until several days after the stigmas dried and nut growth had begun. This cluster produced two nuts, one appeared normally filled, and the other was a mere shell. (2) The bag was put on before the pistillate flowers were receptive and before any pollen had shed, enclosing both pistillate, and staminate flowers in the bag. The bag injured, somewhat, the new growth, and no nuts were produced. (3) Bagged as was number two, and pollinated with pollen from a Robson tree when stigmas appeared receptive. No nuts produced. Two GROUPS OF THE HICORA PECAN 143 (4) Implicate of No. 2, inclosing both sex of flowers. This cluster pro- duced one nut that was normally filled. (5) Duplicate of No. 2. No nuts formed. (6) The catkins were cut from this branch and the cluster of pistillate flowers bagged as in No. 1. One abnormally formed nut, which was a mere shell, was produced. It was about one-fourth normal size and was sharp pointed. (7) Emasculated and bagged as No. 1. This cluster produced one nut that seemed normal excepting that it failed to ripen on time. (8) Emasculated and bagged as No. 1. Produced three normal nut (9) Bagged inclosing sexes of flowers as No. 2 and pollinated with pollen from Robsou when stigmas appeared receptive. One abnormally formed shell lacking any embryo was produced. (10) Same as No. 9 excepting that two instead of one, half size shells without embryo were formed. (11, 12, and 13) Bagged same as No. 2, but no nuts were produced. (14) Emasculated and not pollinated same as No. 1. This cluster pro- duced one nut well filled, but was only approximately half size for this variety, and also one small shell without an embryo. We bagged large numbers of flower clusters of about twenty other varieties in 1916, and got results very/ similar to those above reported. The bags were put on with great care and strict precaution taken to prevent pollination other than that applied by hand as planned; yet we find nuts appearing in bags that were put on before the pistillate flowers were receptive and no pollen allowed to enter. This condition indicates that parthenogenesis exists in pecans as reported by Morris (7) in three species of hickories, and the chinquapin. Hickory-Pecan Hybrids The entire list of tree species that are capable of being hybridized has not yet been determined. Babcock (6) crossed the native walnut of South- ern California (Juglans californica) as the female parent and the coast live oak (Quercus agrifolia) and one of the oak hybrids as a male parent. Nuts from both these crosses produced plants. Some pecan propagators have* propagated and disseminated nut trees which are, in habits of growth, de- partures from the hickory and said to be hybrids between the hickory and the pecan. These have been given the name "Hican." The exact origin of these hicans seems not to be definitely known. How- ever, they vary as much from the pecan as from the hickory and are very probably hybrids between the two species. The chief differences between these supposed hybrids and the pecan is that they, like the hickory, pro- duce their catkins only at the base of the current year's growth, while the pecan sends out its catkins at several nodes along the preceding year's growth. Hickories as Pollinators for Pecans Hickory trees on the Experiment Station grounds, like pecans, could be divided into early and late staminate flowering groups. However, they differ from the pecan in that the catkins are borne only at the base of the new growth and none are conspicuously bracted as are the catkins in Group II of pecans. The two groups among hickory trees do not seem to be confined strictly to species as we found both late and early bloomers among trees of Hicora glabra, and what appears to be hybrids between Hicora fflabra and Hicora alba. The late blooming hickories shed their pollen at about the time that the pistillate flowers of varieties of Group IT of pecans are receptive. 144 GEORGIA EXPERIMENT STATION Two twigs front hickory trees. One on left has shed most of its pollen while the pistillate flowers are hardly receptive. One on right has shed no pollen and the stigmas of the pistillate flowers dried and growth of the young nuts started. Going on the hypothesis that the hickory aud the pecan will hybridize, we attempted to make some crosses between the two species in 1916. Three clusters of pistillate flowers on a Stuart tree were bagged before they were receptive and later pollinated in their receptive stage with hickory (Hicora glabra) pollen. From these crosses we secured two nuts, yet in view of our 1915 experiences we are not sure whether these nuts are the .result of the hickory-pecan cross or whether they are parthenogeuic devel- opments. If these nuts are the result of the hickory pollen we have some explanation to offer for pecan varieties of Group II producing nuts in close proximity to hickory trees when they would be either partially or wholly self sterile if grown in absence of pollen other than their own production. Varieties Recommended for Planting If varieties of Group II are self-sterile when planted alone, varieties of Group I should be planted in close proximity to insure successful pollination. Before making recommendations of methods for arranging the varieties of the two groups in planting so as to make pollination more certain, we thought it best to supplement varietal data from the Experiment Station plat with the recommendations of commercial pecan growers in different sections of Georgia as well as from a few sections of neighboring states. This is done for two reasons, first, because the Experiment Station is located in the Piedmont section of the State where some commercial varieties are thought not to do well ; and second, for the purpose of eliminat- ing personal preferences by getting preferences of a considerable number of growers. To secure this data a circular letter was sent to sixty pecan growers with the request that they name six varieties best suited to their respective localities. In some instances more than one choice is given from a locality which shows personal preferences of different growers. Most of the grow- ers gave the varieties in order of preference. The following table gives the varieties from the different localities in the same order as given by the growers. \ Two GROUPS OF THE HICORA PECAN 145 'Iff a fl !?? S S3 S <5 J S 2 O5 CO I OQ II fl > > fe > bi B -9 -S -g o 02 OQ 02 CO PH Q 1 S O O 146 GEORGIA EXPERIMENT STATION "ill!!* Iff! I U Cu g ce Cu t> ccOoQw in . H 2 t .2 Q t: I I I I 1 1 I 1 I I 1 S 5 ^ - HIS!!! ' 'iil TWO GROUPS OF THE HlCOKA PECAN 147 From the above table it will be observed that Schley, Stuart, Delnias, Van Deman and Moneymaker of Group II are very popular among the growers while Success, Pabst, and Alley are popular varieties of Group I. Yet there are other varieties in the table that are preferred in varying degrees and should be planned for in grouping for successful pollination. Below we give a list of the varieties in each group that have come under our observation. From these the grower can select such as he likes and group them so that the varieties of Group I, the early bloomers, can be so planted as to serve as pollinators for varieties of Group II, the late bloomers; or cions from varieties of one group may be top worked onto a few limbs of the other group and in this way one tree will rep- resent both groups. Varieties of Pecans Group I. ' Group II. Alley Appomattox Beverage Triumph Atlanta Centennial Bradley Georgia Giant Capital Haven Curtis Jerome Delmas Mantura Frotscher Mobile Hadley Moore Moneymaker Nelson Pan-American Pabst President Randal Russell Robson Russell No. 2 Rome Stuart San Saba Teche Success Van Deman Washington Waukenah Young Below is given an outline suggesting methods of planting the trees of the two groups : Group 1 X X X X X X X Group 2 X X X X X X X Group 2 X X X X X X X Group 1 X X X X X X X Group 2 X X X X X X X Group 2 X X X X X X X Group 1 X X X X X X X We give two rows to be planted to varieties of Group II to each one row of Group I, primarily for the reason that most commercial growers give first and second place to the varieties of Group II. In grouping varieties including Alley and Moneymaker, it is well that these two varieties be planted near each other for the reason that Alley sheds its catkins before all the pistillate flowers pass the receptive stage and that the Moneymaker is one of the earliest bloomers of Group II and will serve as a pollinator for the Alley. CONCLUSIONS 1. Varieties of pecans can be divided into two distinct groups based on their floral characters. 2: Varieties of Group I shed their pollen at about the same time the majority of the pistillate flowers become receptive. 233133 Thi -"k is DUE on the last date stamped below 148 GEORGIA EXPERIMENT STATION 3. Varieties of Group II shed their first pollen after most of the pistillate flowers pass through the receptive stage. 4. On the whole, the varieties of Group I are apt to be self-fertile, while those of Group II are apt to be self-sterile. 5. Varieties of both groups product viable pollen. 6. Phenological data from varieties grown in South Georgia agree fairly closely, as regards the two groups, with that from the varieties at the Experiment Station. 7. Native hickory trees in the vicinity of Experiment, Ga., could be divided into early and late staniinate flowering groups. 8. It is probable that the hickory will serve as a pollinator for the pecan. 9. Self-sterility of a variety may be expected in proportion to the interval between the receptive stage of the pistillate flowers and the shedding of the pollen 10. Mechanical injury to catkins before the date of normal shedding of pollen may partially prevent self-sterility among varieties of Group II. 11. Parthenogenesis in pecans is indicated. 12. Varieties from Group II should be planted in close proximity to varieties from Group I to insure successful pollination. ACKNOWLEDGMENT Grateful acknowledgment is due the following: Mr. J. Slater Wight, of Cairo, Ga., for supplying phenological data given in Table 3. Mr. H. C. White, Putney, Ga. ; Mr. G. H. Tomlinson, Putney, Ga. ; Mr. J. B. Wight, Cairo, Ga. ; Mr. B. W. Stone, Thomasville, Ga., tor allowing the use of their orchards for making observations and supplying floral material for laboratory studies. A large number of growers in various sections of the pecan belt for making recommendations of varieties suitable for their respective localities. Dr. B. B. Higgins, Botanist and Plant Pathologist of this Experiment Station for making drawings of tetrad (Fig. 6) ; for making microphoto- graph (Fig. 4) and for helpful suggestions and criticisms of the manuscript. REFERENCES ( 1 ) Stuckey, H. P. Ga. Exp. Sta. Ann. Kept. 1915. ( 2 ( Bailey, L. H. Report of the Horticulturist. Mich. Agr. Clo. Bull. 31:1-96. 1887. The Cultivated Native Plums and Cherries. N. Y. Cornell Exp. Sta. Bull. 38:1-73. 1892. ( 3 ) Beach, S. A. The Self -Pollination of the Grape. Gard. and For. 5:451-452. 1892. - Notes of Self-Pollination of the Grape. N. Y. State Exp. Sta. Ann. Kept. 597-606. 1892. The Fertilization of Flowers in Orchards and Vineyards. N. Y. Sta. Ann. Kept. 13 :633-648. 1894. - Production of Grapes as Affected by Self- Fertilization of Their Blossoms. N. Y. State Sta. Ann. Kept. 14:320-325. 1895. - Self- Fertility of the Grape. N. Y. State Exp. Sta. Bull. 157:397-441. - Fertilizing Self-Sterile Grapes. N. Y. State Exp. Sta. Bull. 169: 331-371. ( 4 ) Waite, M. B. The Pollination of Pear Flowers. U. S. Dept. Agr. Div. Veg. Phys. Path. Bull. 5:1-86. - Sterility in Japanese Plums. Am. Agr. 75:112. 1905. (5) Waugh, F. A. The Pollination of Plums. Am. Pom. Soc. Kept. 25:86-94. - The Pollination of Plums. Vt. Exp. Sta. Bull. 53:45-65. - Problems in Plum Pollination. Vt. Exp. Ann. Kept. 11:238-262. Further Work in Plum Pollination. Vt. Exp. Sta. Ann. Kept. 13: ">55-362. - Pollination of Apples. Vt. Exp. Sta. Ann. Kept. 13:362-366. (6) Babcock, E. B. Walnut-Oak Hybrid Experiments. Amr. Breeders' Mag. 3: 200-202. 1910. ( 7 ) Morris, R. T. TTnusual Methods of Propagating Nut Trees. North. Nut Grow- ers' Assoc. Proc. 4:45-48. 1913. ( 8 ) Ramsey. F. T. My Experience with English Walnuts. The Nut Grower, XV. ( 9 ) Berckmans, P. J. Ga. State Hort. Soc. Proc. 27th Ann. Rept : P. 46. (10) Lewis, C. I. Walnut Culture in Western Oregon. 1916. UWrVERSKTY of O AT TXttt AX1<'IT) i s OF-CAllFOJfcfc % I 5 -OF-CAllFOffx ,\\\E-M!VER i = I 3 9 = CZ < I s I 3 ^ ^ %)JI1V3-JQ | 1 ?n ^ P 1 3 5 s \ 4 S ^sUB-MGBfb S J >0 L S 1 ^^ & * ? * University of California Los Angeles filiilR L 006 855 1480 fiilllli AA 000724253 o