SENSITIVE STAMENS IN PORTULACA. 465 
tact with the stigmas of the next flower visited. The stigmas are 
however raised considerably above the tops of the stamens, which 
may sufficiently guard against self-fertilization, and as they di- 
verge quite widely it is possible that they are touched by insects 
before the stamens are. 
Hoping to get more light on this point I examined with much 
care a large number of flowers of Claytonia Virginica with the 
following results : 
e stamens of Claytonia (this species, at any rate) are not 
sensitive,—or at least not appreciably so. They however have a 
motion which appears to accomplish the same probable result, 
namely, the securing of cross-fertilization. When the flower first 
opens, its five stamens rise parallel with the three cleft style, and 
at this time the anthers may or may not be shedding their pollen, 
but the stigmas are closed, the three stigmatic surfaces being 
closely applied to each other so that the style appears as if entire 
and single. After an undetermined time the lobes of the style 
begin to diverge, and the stamens then, or a little before, recede, 
so that when the stigmas are fully exposed the anthers are turned 
back as far as the opposite petals will allow them to be. In the 
majority of casés the stamens seem to bear with considerable 
force upon the petals, the anthers touching nearly the middle 
point of the petals, while the filaments are arched as in Kalmia 
glauca. 
From my observations I am led to think that after fertilization 
has taken place the stamens regain to a greater or less extent 
their first position—though of this I cannot speak with certainty. 
he arrangement here seems to be beyond a doubt for preventing 
self-fertilization, and I have no doubt that had time permitted, 
some contrivance for securing the interchange of pollen would 
have been found. This must however be left for the next spring’s 
examinations. 
AMERICAN NATURALIST, VOL. VII. 30 
