138 TENDRIL-BEARERS. Cuar. IV. 
taneously from side to side; and on a very hot day, 
one made two elliptical revolutions, at an average rate 
of 2hrs.15 m. During these movements a coloured 
line, painted along the convex surface, appeared after 
a time on one side, then on the concave side, then on 
the opposite side, and lastly again on the convex side. 
The two branches of the same tendril have independent 
movements. After a tendril has spontaneously revolved 
for a time, it bends from the light towards the dark: 
I do not state this on my own authority, but on that 
of Mohl and Dutrochet. Mohl (p. 77) says that in a 
vine planted against a wall the tendrils point towards 
it, and in a vineyard generally more or less to the 
north. 
The young internodes revolve spontaneously; but 
the movement is unusually slight. A shoot faced a 
window, and I traced its course on the glass during 
two perfectly calm and hot days. On one of these 
days it described, in the course of ten hours, a spire, 
representing two and a half ellipses. I also placed 
a bell-glass over a young Muscat grape in the hot- 
house, and it made each day three or four very small 
oval revolutions; the shoot moving less than half an 
inch from side to side. Had it not made at least three 
revolutions whilst the sky was uniformly overcast, I 
should have attributed this slight degree of movement 
to the varying action of the light. The extremity of 
the stem is more or less bent downwards, but it 
never reverses its curvature, as so generally occurs 
with twining plants. 
