500 Harris . — On a Chemical Peculiarity of the 
Upon the opening of the flower the filaments of the smaller stamens 
turn somewhat upwards, while the pistil is turned in the opposite direction, 
downwards, for the greater part of the length, but the tip is turned somewhat 
upward. The larger stamens bend outward proximally but curve in distally, 
bringing the large anthers towards each other. 
These large anthers open by two introrse longitudinal slits soon 
(perhaps half an hour) after anthesis ; their pollen forms two bright green 
or yellowish-green lines, in sharp contrast to the reddish ground colour 
of the anther, which darkens with age. The pollen is very freely and 
readily shed, adhering to any object brushed lightly against the surface of 
the opened anther. 
The smaller anthers do not dehisce until about half an hour after the 
red ones ; their pollen does not leave the cells so rapidly, and when 
examined microscopically generally does not appear as much shrunken by 
drying. 
The red anthers fall first, generally about eight or ten hours after the 
flower opens. The yellow anthers often remain on the filaments until the 
second day. As far as observed, both types fall spontaneously. No insect 
has been observed eating entirely either type, as has been described for 
some other forms of pollen flowers. 
III. Physiological Peculiarities of the Anthers. 
The difference in the time of dehiscence of the two types of anthers, 
the fact that the larger anthers seemed to fall before the smaller, and 
especially the observation that their pollen seems more dry and powdery, 
and when microscopically examined appears more shrunken, suggested the 
desirability of more detailed and accurate observations to determine the 
nature of these phenomena. 
The most plausible explanation for the peculiarities observed would 
seem to be a difference in the rate of evaporation of water. Two simple 
experiments proved the correctness of the hypothesis, (a) When red and 
yellow anthers were placed close together on a slide and their pollen 
crushed out simultaneously and spread out over the glass and examined 
under the microscope, the pollen from the red anthers dried more rapidly 
than that from the yellow, (b) The necessity of the frequent readjustment 
of the balance on the pans, of which lots of red and yellow anthers were 
exposed to the air in watch-glasses, showed that the two lots were decreasing 
in weight at different rates, and that the red anthers were losing more 
rapidly than the yellow. 
A series of careful parallel weighings was then undertaken to determine 
as nearly as possible the difference in the rate of evaporation . 1 
1 There are two possible sources of error in my work. All my material came from plants kept 
under glass in winter and transferred to the open for the summer. This might, as Darwin suggested 
