1915] BARTLETT—MUTATION IN OENOTHERA 95 
linear-lanceolate. The stems were simple. No. 7 died just 
before flowering, when only 7 cm. high. No. 12 flowered at a 
height of 1ocm. The ovary was 7 mm. long; hypanthium 10 mm. 
long; calyx segments 4 mm. long, excluding the distant free tips, 
which were 1 mm. long. The calyx differed from that of the typical 
form not only in having distant calyx tips, but also in being densely 
soft-pubescent. Unfortunately, this plant was sterile and pro- 
duced no seeds. As far as the writer is aware, mut. pusilla repre- 
sents the extreme of nanism in the subgenus Onagra. 
With a single exception, the 7 suspected dwarfs developed as 
quite normal plants, indistinguishable from the mass of the culture. 
One plant, no. 10, differed from the rest in that it had stiff, distant 
calyx tips 5 mm. long which were continued on the angles of the 
squarish bud as a marked carina. The buds were almost glabrous, 
as in the type form of the culture, but in marked contrast to some 
of the other mutations. This plant was self-sterile, but produced 
abundant seeds when pollinated with typical O. pratincola. 
The Lexington C culture which was grown to maturity in 
1913 included, besides the 9 plants from the first sowing and the 
mutations and suspected mutations of the second sowing, all the 
plants from two pans in which there appeared to be no variation. 
There were 72 of these plants, nos. 23-94.%% When they matured 
two mutations were found which had not been detected in the 
early seedling stages. With these two exceptions, the plants were 
absolutely uniform among themselves, and exactly the same as 
Lexington A, Lexington B, and Lexington E. (Of each of these 
three strains 30 plants were grown to maturity.) The two muta- 
tions were not alike and were different from any of the other new 
types which had been obtained. Both, however, were almost 
8 The culture numbers of these plants are all given here in order to avoid lengthy 
repetition in subsequent papers which will deal with the same strains. It may be 
well to explain that every plant in the writer’s garden is designated by the name of 
the strain (for which a number has often been substituted) followed by a succession 
of numbers which indicate the pedigree and number in the culture of each individual. 
Subscripts are used when it is wished to distinguish between sister plants grown in 
different years, or to indicate the years in which the successive generations were 
grown. “Lexington C-11,;,” for example, would be the complete designation of the 
plant of mut. xummularia which is shown in fig. 6. Plants of the F, generation, grown 
i T1914, would be “Lexington C-11,;-11,,” “Lexington C-11-2,” etc. 
