162), are given on p. 385: one
of the shoots, from which the photographs were taken, was accidentally bent
to one side.
Fig. 163. Nicotiana tabacum: circumnutation and nyctitropic movement of a
leaf (5 inches in length), traced on a vertical glass, from 3 P.M. July
10th to 8.10 A.M. 13th. Apex of leaf 4 inches from glass. Temp. 17 1/2o -
18 1/2o C. Figure reduced to one-half original scale.
At the base of the petiole of N. tabacum, on the outside, there is a mass
of cells, which are rather smaller than elsewhere, and
[page 387]
have their longer axes differently directed from the cells of the
parenchyma, and may therefore be considered as forming a sort of pulvinus.
A young plant of N. tabacum was selected, and the circumnutation of the
fifth leaf above the cotyledons was observed during three days. On the
first morning (July 10th) the leaf fell from 9 to 10 A.M., which is its
normal course, but rose during the remainder of the day; and this no doubt
was due to its being illuminated exclusively from above; for properly the
evening rise does not commence until 3 or 4 P.
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