1915] BARTLETT— MUTATION IN OENOTHERA 97 



plants, and very brittle. A few seeds were obtained from this plant 

 by self-pollination, but they did not germinate. 



The 729 plants of Lexington C which were grown in 1913 yielded 

 in all 6 different mutations. All of them except mut. nitida and 

 mut. nummularia were infertile or nearly so to their own pollen. 

 The latter type, in spite of the fact that it was unwittingly sub- 

 jected to very unfavorable conditions, produced seeds from which 

 a second generation has been grown. For fear of losing the 6 

 original plants, they were planted in the center bed of the green- 

 house when the rest of the culture was transferred to the 

 garden. Before it was realized how much their development 

 was being retarded by the extreme heat in the greenhouse, it was 

 too late to move them again with any prospect of success. 

 Three plants died after they had begun to flower, but before any 

 seeds were ripe. 



The characters of mut. nummularia 



A few plants of typical 0. pratincola which were kept in the 

 greenhouse with the mutation served to show that there are distinct 

 differences in the habits of growth of the two types, when they 

 are grown under identical conditions. This fact will be apparent 

 from fig. 7, in which two sister plants of the same age are shown. 

 It will be noticed that the stature of the mutation is less than that 

 of the parent type, but that the lateral branches are more numer- 

 ous and more densely leafy. A thoroughgoing comparison of the 

 two types cannot be made until the cultures of 1914 shall have 

 grown to maturity out of doors. The more striking contrasting 

 characters, however, are the following: 



In O. pratincola In mut. nummularia 



The early seedling leaves are ovate. The early seedling leaves are orbicu- 

 lar. 



The stem leaves are reflexed. The stem leaves are involute. 



The lower leaves of the lateral The lower leaves of the lateral 



branches are ovate-lanceolate. branches are broadly ovate. 



The ovary and calyx are sparsely The ovary and calyx are closely and 



pilose (sometimes almost glabrous). finely pubescent. 



