Vines • — On Epinasty and Hyponasty. 421 
light and gravity. The general method of experimentation 
was the following. Plants were placed in darkness in the 
normal position, and the effect of these conditions upon the 
position of the leaves or other dorsiventral members was care- 
fully noted at intervals of generally twenty-four hours. Other 
similar plants were rotated on the clinostat in darkness, and 
the effect observed as in the former case. By comparing the 
behaviour of the members in the two cases, it was possible to 
draw some conclusions as to the influence of gravitation upon 
the growth of the members under observation. All the plants 
were grown in pots ; and, when on the clinostat, were so placed 
that the long axis of the plant coincided with that of the 
machine. 
It will be convenient to arrange my observations according 
to the results which I obtained ; that is, in accordance with 
the more striking epinastic or hyponastic growth. 
1. Observations on Epinastic Members. 
These observations were all made on dorsiventral foliage- 
leaves. The following is a typical case. A seedling of 
Helianthus annuus , about 40 cm. high, with four whorls of 
leaves (generally three leaves in each whorl in the plants 
used), in addition to the cotyledons and the apical bud, had 
been grown under normal conditions and fully exposed to 
light. Hence, at the beginning of the experiment, the leaves 
were approximately horizontal. The effect of being kept for 
twenty-four hours in darkness in the normal position was that 
the leaves of the upper whorls, especially the second and 
third, showed a strongly marked downward curvature. In 
the younger leaves this curvature extended throughout the 
whole length of the leaf from the apex to the insertion ; in 
the older, but still growing leaves, the curvature was confined 
to the petiole. The oldest leaves, having ceased to grow 
showed no change in position. 
The remarkable difference in the appearance of the plant, 
F f 2 
