SENSITIVE STAMENS IN PORTULACA. 
BY PROFESSOR C. E. BESSEY. 
Two years ago my attention was first called to the sensitiveness 
of the stamens of Portulaca grandiflora, by observing a peculiar 
motion in them, while a small wild bee was engaged in gathering 
honey, and perhaps pollen, from the flowers. Upon trial I found 
that I could, by touching the stamens, make them move through 
quite considerable arcs of circles. I pursued the investigation 
somewhat farther at the time, but on account of a pressure of 
work was compelled to drop it. Last year I again made some 
examinations which confirmed my previous observations, but de- 
clined calling special attention to the facts until I had had oppor- 
tunity for examining Claytonia as well. This last I have been 
enabled to do this spring, and having now again verified my 
_ observations on the Portulacas can give the results. 
In both the common species of Portulaca i.e., grandiflora and. 
oleracea, if the stamens are brushed lightly in any direction, they 
will immediately with a strong impulse bend over toward the 
point from which they were brushed; for example, if a pin be 
made to pass through the stamens from left to right, they will 
bend from right to left; if the direction of the pin be now E 
versed so as tọ pass from right to left the stamens will spring 
back from left to right, and this reversal of motion may be con- 
tinued for some time, of course with diminished energy- 
motion seems to be induced by a pushing or bending of the sanS 
as simply touching it appears not to affect it at all, and the direc- 
tion of this motion seems to be determined by, and always med 
trary to, the pushing and bending. The object of this is, I think, 
evident. When a small insect visits the flower and struggies 
through the thicket of stamens, as it bends them away from itself, 
they will react and bend closely against the sides of the insect’s 
body, covering it with pollen, which will be thus carried from 
flower to flower. Thus far I have not noticed any special arrange 
ments for providing that the pollen of any flower shall not fertilize 
its own ovules; nor have I found any contrivances for certainly : 
making the pollen deposited on the body of an insect come in con- 
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