No. 538] MUTATION IN (EN OTHER A 



595 



is on the average somewhat larger than 0. grandi flora 

 from Alabama grown under the same conditions. The 

 same thing is shown by the measurements of Miss Vail. 

 I should first point out that in all the Oenotheras the 

 flowers in the early part of the season are uniform in 

 size, but towards the latter part of the blooming-season, 

 with dwindling vitality they steadily decrease in size 1 

 until the latest-blooming flowers in 0. Lamar ckiana, for 

 example, have petals no larger than 0. biennis. The 

 style in 0. Lamarckiana does not, however, decrease in 

 length at as fast a rate as the petals, the result being 

 that in late-blooming flowers it not infrequently pro- 

 trudes from the unopened bud. But there is no time in 

 0. Lamarckiana (in my cultures) when the "base of the 

 stigma lobes is slightly below the tips of the anthers." 

 Davis's Fig. 18 ('11) is misleading as a typical flower of 

 0. Lamarckiana, its petals being much too small. He 

 states (p. 216) that the hybrid whose flowers are 

 "scarcely distinguishable from those of 0. Lamarcki- 

 ana" has petals 2.2 cm. long. By choosing flowers 

 towards the end of the blooming-season it will be pos- 

 sible to find petals of any desired size, down to that of 

 0. biennis itself, but in stating the size of petals for 

 comparison with 0. grandiflora, it is only fair to choose 

 the typical flowers which are characteristic of the greater 

 part of the season, and which 0. biennis never produces. 

 MacDougal ('03) states the length of the petals in 0. 

 Lamarckiana to be 4-5 cm., and Miss Vail in 0. grandi- 

 flora ('07, p. 66) 3.5-4.0 cm., which agrees with my cul- 



may sometimes be slightly shorter than in 0. grandiflora) 

 or size of petals, but is almost in agreement with 0. 

 grandiflora in both these characters. As already pointed 



tnres, while in Gray's Ma 



0. Lamarckiana have been 

 the whole larger, than in 

 ana is therefore not intern 

 0. grandiflora, either in lei 



of 0. grandi- 

 the flowers of 



