Xo. 560] GENETIC AL STUDIES ON OENOTHERA 453 



1. F 3 Generations in the Family from the Fj Hybrid 

 10.30La 



The F, hybrid plant designated 10.30La has already 

 been described and figured (Davis, '11, pp. 211-213, Figs. 

 9, 10, 11), and a brief account of its F 2 generation was 

 given in my last paper (Davis, '12a, pp. 410-413). The 

 plant was the result of the cross grandiflora B X bi- 

 ennis A, the latter parent being a rather small-flowered 

 race of biennis from Woods Hole, Massachusetts. The 

 F 2 generation from 10.30La consisted of 1,451 plants, 

 among which could be readily selected at an early stage 

 of development a group of 141 rosettes much smaller 

 than those constituting the mass of the culture and 

 sharply distinguished by their strongly etiolated leaves 

 of a narrower form. From these etiolated rosettes de- 

 veloped a class of dwarfs, the later foliage of which out- 

 grew the etiolated peculiarities of the young plants and 

 became green. The normal green rosettes constituting 

 the mass of the culture presented a remarkable range of 

 form, but inclined more towards the female parent of the 

 cross, grandiflora B. 



A large proportion of the plants, at maturity, were 

 fairly close to the F 1 hybrid plant 10.30L«, but there was 

 presented a wide variation from this form with a mark- 

 edly greater tendency towards the grandiflora parent 

 type. Although the range of variation clearly indicated 

 a process of segregation in this F 2 generation, it was a 

 segregation modified by a general progressive advance 

 in the size of the plant organs. Thus, with respect to 

 flower size, the culture gave a large number of plants 

 (about 50) with flowers as large as or larger than the 

 grandiflora parent, while the smallest flowers represented 

 were 2-4 times larger than those of the biennis parent. 

 The leaves throughout the mass of the culture were, as 

 a whole, larger than those of the parents of the cross and 

 generally distinctly crinkled. 



It should be recalled (see Davis, J 12a, p. 412) that a 



