DEPARTMENT OE EXPERIMENTAL EVOEUTION. 93 



Studies in Vegetable Teratology. — In their bearing upon problems of muta- 

 tion and fluctuating variation, series of teratological forms are of considerable 

 interest. Experimental and statistical studies on proliferation of the fruit in 

 Passiflora and Capsicum, and on seedling abnormalities in Phaseolus are 

 being carried out by Dr. Harris. Extensive cultures of Passiflora and smaller 

 series of Capsicum are being grown and their fruits dissected and classified. 

 During the year about 40,000 bean seedlings were grown in the greenhouse to 

 a sufficiently advanced stage of development to permit necessary determina- 

 tions concerning abnormalities, and selected types have been transferred to 

 the garden for inheritance studies. 



CELL STUDIES IN HEREDITY. 



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



The work upon the somatic chromosomes of the Oenotheras, begun in 1907 

 and reported upon in the two preceding Year Books, has been continued 

 throughout the present season. As the problem requires a thorough knowl- 

 edge of the vegetative characters and life-history of each individual plant, 

 attention has been given exclusively to this study since the germination of the 

 first seed and will be continued until the end of the flowering season. The 

 winter months, as heretofore, will be devoted to the study of the chromo- 

 somes. 



Of especial interest are the progeny derived from the artificial self-pollina- 

 tion of four offspring of Oenothera lata 2X0. gigas $ , 1908. Of these. No. 

 3378, resembling lata, produced 12 offspring; No. 3368, resembling gigas, 52, 

 and No. 3375, a plant with gigas number of chromosomes, but having some 

 vegetative characters that resembled the female parent, 109. Five or six fix- 

 ations of root-tips have been made, from each of these 173 plants for chro- 

 mosome study; all have been carefully measured and described at regular 

 intervals and many photographed in rosette and flowering stages. 



Particular attention has been given to the F^ offspring of O. lamarckiana 9 

 X O. gigas $ , derived from a single pair of pedigreed parents by means of 

 guarded artificial cross-pollination. Each plant was also artificially self-fer- 

 tilized and the offspring grown on either side of the hybrids in the garden for 

 comparison with the latter (40 lamarckiana, 31 gigas). Observations were 

 recorded in detail throughout the season, preservations made for bud, flower, 

 and leaf measurements, and fixations for chromosome studies. Many also 

 were photographed in various stages of development. Since lamarckiana is 

 characterized by the presence of many basal branches (ordinarily 12 to 18, 

 sometimes as many as 22) and gigas by their complete absence or presence in 

 limited numbers (commonly not exceeding 3 in my cultures), this character 

 became important in the study of inheritance among the progeny of this cross. 

 Therefore 31 offspring were grown from seed of one artificially self-polli- 

 nated branched gigas having two basal branches and 31 from an unbranched 

 individual. 



Lata does not ordinarily mature pollen ; but by opening several dozen 

 buds daily for a week during the height of the flowering season enough pollen 

 may occasionally be secured to artificially self- fertilize a flower. In this 



