M. 16th. Tracing not much magnified, as apex of
leaf stood only 5 ? inches from the glass.
(3.) Crambe maritima (Cruciferae, Fam. 14).--A leaf 9 ? inches in length on
a plant not growing vigorously was first observed. Its apex was in constant
movement, but this could hardly be traced, from being so small in extent.
The apex, however, certainly changed its course at least 6 times in the
course of 14 h. A more vigorous young plant, bearing only 4 leaves, was
then selected, and a filament was affixed to the midrib of the third leaf
from the base, which, with the petiole, was 5 inches in length. The leaf
stood up almost vertically, but the tip
[page 229]
was deflected, so that the filament projected almost horizontally, and its
movements were traced during 48 h. on a vertical glass as shown in the
accompanying figure (Fig. 95). We here plainly see that the leaf was
continually circumnutating; but the proper periodicity of its movements was
disturbed by its being only dimly illuminated from above through a double
skylight. We infer that this was the case, because two leaves on plants
growing out of doors, had their angles above the horizon measured in the
middle of the day and at 9 to about 10 P.
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