Vines . — On Epinasty and Hyponosty . 419 
tions of directive forces, such as heliotropism, epinasty, etc., 
but is, on the contrary, the expression of a special heliotropic 
property. He shows that the weight of the leaves does not in 
any way affect their movements, and ascertains, by clinostat- 
experiments in darkness on Phaseolus , Dahlia , Fuchsia , and 
other plants, that when leaves are unaffected by any external 
directive influences, they exhibit well-marked longitudinal 
epinasty. It is not necessary to go into all the details of the 
paper, as they deal chiefly with torsions, a part of the subject 
into which I do not propose to enter at present. It need only 
be noted that he considers the leaves of Dahlia to be nega- 
tively geotropic. 
Coming now to my own observations, I must premise that 
the general method of experiment was arranged, and many of 
the experiments made, before I was aware of the publication 
of Krabbe’s paper. The object in view was to ascertain (1) 
whether epinasty and hyponasty are spontaneous movements, 
or are induced by light or other causes as stated by Detmer ; 
and (2) whether the curvatures of dorsiventral members which, 
as pointed out in the foregoing historical sketch, have been 
hitherto ascribed to negative geotropism, are or are not due 
to this cause. I may at once give the conclusions to which 
I have been led: (1) Epinasty, and also hyponasty, are not 
induced, but are spontaneous movements ; (2) dorsiventral 
members, so far as my experiments go, are not negatively 
geotropic, the movements hitherto ascribed to negative geo- 
tropism being due to hyponasty, and altogether independent 
of the action of gravitation. 
The first series of experiments . were extremely simple. 
Detmer based his theory of photo-epinasty on the observa- 
tions that (1) the cotyledons of seedlings of Cncurbita re- 
mained closed up, with their upper surfaces in contact, when 
kept in continuous darkness for ten days, but they at once 
began to separate when, at this age, the plants were exposed 
for three to five hours to bright diffuse light ; and (2) that the 
laminae of the primordial leaves of Phaseolus , kept in con- 
tinuous darkness for fourteen days, presented a folded or 
F f 
