No. 560] GENETIC AL STUDIES ON OENOTHERA 



From the mass of rosettes with characters as illus- 

 trated in Fig. 7, 12.55a, a group of 8 dwarfs (Fig. 7, 

 12.55 ra) was quickly recognized. One can hardly im- 

 agine a much sharper contrast between rosettes in the 

 same culture than is shown in this illustration (Fig. 7, 

 12.55m compared with 12.55a). By the side of the dwarf 

 12.55m is a rosette, 12.59a, of the F 3 from one of the 

 dwarfs of the F 2 , 11.42m (similar to Fig. 5). A com- 

 parison will show how perfectly the F 2 type 11.42/ (Fig. 

 6) has repeated the behavior of its parent hybrid F, plant 

 10.30L& in throwing off a class of similar dwarfs. The 

 8 dwarfs of the culture 12.55 were set out under con- 

 ditions ill-suited to their constitution and I had great 

 difficulty in saving 5 plants from a period of drought. 

 These are now in the hot house, where it is hoped that 

 they may be brought to maturity. 2 



The normal rosettes of the F 3 culture 12.55, excluding 

 the 8 dwarfs described above, developed a fairly uniform 

 set of plants which at maturity exhibited a foliage of 

 broader and more crinkled leaves than those of the F 2 

 parent hybrid 11.42/. This progressive advance in foli- 

 age was also supplemented by a greater vigor and size of 

 the plants, although the flowers remained without marked 

 change. Summarizing the behavior of the F 2 plant 11.42/ 

 in the F, generation, the most striking points were the 

 repetition of the behavior of the F, parent hybrid 10.30L& 

 in throwing off the same types of dwarfs, and a much 

 greater uniformity among the normal plants with appar- 

 ent advance in leaf size and vegetative vigor. 



The next form to be considered is a plant, 11.42a, which 

 was fairly representative of the mass of the F 2 genera- 

 tion from 10.30L/;. This plant (Davis, '12a, p. 415, 

 11.42.a) was 1.5 m. high and characterized by large flowers 

 (petals about 4 cm. long) and large crinkled leaves (Fig. 

 8). It was a type rather common and intergrading with 

 other forms of the culture. It exhibited a decided pro- 

 gressive advance in flower and leaf size over the F, 



J Of the 5 dwarfs 3 are now (June 1, 1913) almost full grown and true 

 to the type. 



