82 
seeds by the lateral pressure which the valves exert as they fold 
lengthwise, but in the case of Claytonta Virginica,a much more 
complicated method of expulsion seems to be necessary ( Figs. 
11-15). The round, flat seeds, six in number, are arranged sys- 
tematically in the capsule, and as the valves curl inwardly and 
press against them, the uppermost one (a, Fig. 13), is expelled 
as soon as the pressure becomes great enough. After the expul- 
sion of the first seed, those remaining are arranged again, 
‘loaded ” for a second bombardment, and the seed @ is shot out. 
In this way the entire number is expelled from the capsule, the 
last one by the pressure from the sides of the valves. If ripe 
specimens of this plant be placed in a dry room on sheets of 
paper, the rattle of the bombardment can be distinctly heard 
and the floor will be strewn for several feet with the shining 
seeds. Singular as it may seem in a case of this kind, where so 
much force is displayed, moisture seems to have little effect upon 
the capsules when once dried—perhaps because their office to 
the plant is performed when the seeds are thrown. 
Hybiscus Syriacus, ( Figs. 16,17), has membranaceous cap- 
sules, which are retained upon the plant long after the seeds have 
been blown away, and the wide and rapid variations in the posi- 
tion of the valves make it a most interesting case; in fact, so 
pronounced are these changes that after a sharp rain the whole 
aspect of the plant is notably altered. These capsules are rep— 
resentative of a large class of membranaceous seed vessels, of which 
Hypericum Ascyron, ( Figs.18, 19), and Dictamnus Fraxinella 
(Figs. 33, 34), furnish examples. These capsules close when placed 
in water, in from five to fifteen minutes, varying with the species 
and maturity of the pods. 
The long, soft pods of the Asclepiads, if examined upon a 
rainy day, will all be found closed or nearly so. The movement, 
although not rapid is quite marked, on account of the large size 
of the pods. 
From its peculiar curled pods Cassia Chamecrista, ( Figs. 20, 
21), might be expected to show decided hygroscopic movements ; 
if these open or half-open pods are placed in water, they 
close in five or six minutes. Although exhibiting this rapid 
