DEPARTMENT OP EXPERIMENTAL, EVOLUTION. 9$ 



VARIATION AND CORREIvATION IN FERAL PLANTS. 



Dr. Harris has been making comparative biometric studies on species of 

 Cercis, Staphylea, Sanguinaria, Hibiscus, Agave, and Cassia. Extensive col- 

 lections are being made from several habitats and seasons, in order to test the 

 influence of environmental and seasonal differences on variation and correla- 

 tion constants, and it is hoped that some of the results will be ready for pub- 

 lication shortly. During the year about 200 tables of data and calculated 

 constants have been prepared. Probably these habitat investigations will form 

 the basis of transplantation investigations to be undertaken later. 



CELL STUDIES IN HEREDITY. 



These were continued by Miss Lutz, who reports as follows: The work 

 upon the chromosomes of the somatic cells of the Oenotheras in 1907, reported 

 upon in Year Book No. 6, has been continued throughout the present year on 

 a much more extensive scale. 



The investigations of the preceding year having revealed the number of 

 somatic chromosomes for Oenothera gigas to be approximately double that of 

 any other form so far studied, the opportunity was at once suggested of se- 

 curing valuable data upon the question of the behavior of chromosomes in 

 inheritance by crossing gigas with a form having the smaller number. Only 

 3 offspring of 0. lata female X O. gigas male were available for study the 

 first summer, but these showed such remarkable combinations of chromo- 

 somal and vegetative characters that it was decided to repeat the cross upon 

 a larger scale the following season. Accordingly seeds were sown and yy 

 seedlings obtained, all of which were transplanted to the experimental gardens 

 in May. Representative types were photographed in early rosette and late 

 rosette and flowering stages — 107 exposures in all — about one- fourth of which 

 were of plants connected with work upon other problems. 



Fixations were made of root-tips of 50 of the yy hybrids in the early rosette 

 stages, and 35 of these have been carefully studied and chromosomes counted. 

 In connection with the microscopical investigations, the vegetative characters 

 of the hybrids were closely observed daily from time of germation to close 

 of flowering season, and continuously observed from 5 a. m. until y^ 30™ p. m. 

 daily from July i to September i. The results of these investigations will be 

 published shortly. 



Owing to the scarcity of pollen produced by these hybrids, seeds were ob- 

 tained only after the most persistent efforts at artificial self-pollination for six 

 weeks following the opening of the first flower. Although the seeds have not 

 been harvested, it is believed that by this means guarded self-pollinations 

 were secured of the representative types of hybrids, and in a number of cases 

 reciprocal crosses with gigas. These second-generation offspring will form 

 the chief subject of study for 1909. 



