396 BOTANICAL GAZETTE [JUNE 
NUTATION OF THE GROWING PLANT. 
The observations were commenced on plants from three to 
five feet high, with stems varying from a half inch to an inch 
and a half in diameter. Observations were taken on a large 
number of individual plants, as well as on large patches of 
plants in general. In the morning, at sunrise, when the weather 
is clear, the plants all nutate toward the east or northeast at an 
angle of 45° to 75° from the vertical. The leaves stand out 
with rigid petioles so that their upper surfaces face the morning 
sun. When one stands looking toward the west, all the termi- 
nal buds and upper leaf surfaces face him. As the sun rises 
from the horizon, the plants gradually become erect and the 
leaves move at the same time so as to present their upper sur- 
faces directly at right angles toward the rays of light. At noon 
the stems and terminal buds are vertical. During the afternoon 
the tops gradually nutate towards the west at an angle of 60° to 
ng 90° from the vertical. Usually the nutation is 90°. The upper 
Surfaces of all the upper leaves have changed their positions so 
that they face due west and all those near the terminal bud have 
thus a more or less vertical position. The bending of the stem 
usually takes place about four or five inches from the tip and 
the curve represents merely the quadrant of the circumference 
of a circle, although sometimes it is more abrupt and angular 
(Jig. 1). 
By about 10 o’clock p.m. most of the stems have reg 
the vertical position, but at this time some may still be curved 
toward the west from 20° to 40°. The leaves now are turned 
downwards, drooping in such a manner that the apices all pom 
vertically toward the earth. The curving is mainly in the petiole. 
This “sleeping” position contrasts quite strikingly with the oy 
position, and it is taken both on cloudy and on starry nights. 
About 2 o’clock a.m., and usually much earlier, the leaves begin 
to be raised, and the tops of the stems turn toward the ae 
gradually until sunrise, when they are again nutating from 45 to 
75° toward the east. 
ained 
