Vines . — On E pinas ty and Hyponasty. 429 
stem, their surfaces being now vertical. By the fourth day of 
the experiment the following changes in position had been 
effected. Of the youngest pair of leaves, the upper had 
recurved so that its upper surface had come to be nearly 
horizontal ; the lower had only slightly changed its position, 
having risen somewhat out of the vertical plane in the acro- 
petal direction. The two leaves of the second whorl both 
exhibited marked epinastic curvature, and their petioles had 
undergone torsion through nearly a right angle, so that, in 
both, the upper surface of the lamina was directed upwards, 
though it was not flat on account of the epinastic curvature. 
Similar results were obtained with H. pubescens and with 
Dahlia variabilis. 
It must be borne in mind, in the interpretation of these 
facts, that the leaves were strongly epinastic, and there can 
be no doubt that the changes in position were due partly to 
this cause and partly to the action of gravitation. If, now, an 
explanation be attempted on the assumption that the leaves 
are negatively geotropic, it will be found to be impossible. 
Taking first the youngest pair of leaves, the upper leaf, being 
vertical, is in the position of stable equilibrium as regards 
negative geotropism ; hence its curvature into the horizontal 
plane must be due to epinasty acting powerfully in opposition 
to negative geotropism. With regard to the lower leaf, 
inasmuch as it could hardly have been absolutely vertical, 
it is probable, on the theory of its negative geotropism, that 
gravitation tended to raise it into precisely the opposite 
position to that in which it was originally placed, and this 
effect was to some extent realized in the observed change of 
position. In this case, then, negative geotropism succeeded 
in overcoming epinasty. But this conclusion is in direct 
contradiction to that arrived at with regard to the upper leaf. 
Inasmuch as the two leaves belonged to the same whorl, they 
must have been in the same epinastic stage of growth ; 
hence, it is impossible to assume that in the one case epinasty 
overcame negative geotropism, whilst in the other negative 
geotropism overcame epinasty. 
