; its apex 9 inches from the vertical glass. Figure
reduced to one-third of original scale. Plant illuminated from above; temp
17 1/2o - 18 1/2o C.
A petiole, which was carefully observed, stood during the day 25o above the
horizon and at night 32o below it; it therefore fell 57o. A filament was
fixed transversely across the terminal leaflet of a fine young leaf (2 1/4
inches in length including the
[page 366]
petiole), and the movement of the whole leaf was traced on a vertical
glass. This was a bad plan in some respects, because the rotation of the
leaflet, independently of its rising or falling, raised and depressed the
filament; but it was the best plan for our special purpose of observing
whether the leaf moved much after it had gone to sleep. The plant had
twined closely round a thin stick, so that the circumnutation of the stem
was prevented. The movement of the leaf was traced during 48 h., from 9
A.M. July 10th to 9 A.M. July 12th. In the figure given (Fig. 151) we see
how complicated its course was on both days: during the second day it
changed its course greatly 13 times.
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