418 Vines . — On Epinasty and Hyponasty . 
forces, such as epinasty,’ is strongly in favour of Frank’s views. 
F. Darwin also confirms Frank’s statement that radical leaves 
are negatively geotropic (apogeotropic), at least in the case of 
Ranunculus Ficaria , and notes also that radical leaves under 
normal conditions are epinastically pressed against the ground. 
Another paper which must be noticed, but which can hardly 
be regarded as contributing much to the elucidation of the 
subject, is that of Detmer 1 . From observations on the effect 
of darkness and light on the expansion of leaves, Detmer came 
to the conclusion that epinasty is not, as De Vries thought, 
spontaneous, but is induced by the action of light ; that it 
is what he terms £ a paratonic nutation-phenomenon.’ He 
therefore suggests that the word ‘ photo-epinasty 3 should be 
substituted for ‘epinasty/ It may be pointed out that he 
omits to refer at all to hyponasty ; but of course if epinasty 
is not spontaneous, it is impossible to avoid the inference that 
the same is true of hyponasty, and the assumption of c photo- 
hyponasty’ is therefore inevitable, though^Detmer does not 
carry out his views to this logical conclusion. 
Vochting 2 has made some interesting observations on the 
assumption of the fixed light-position by the leaves of certain 
Malvaceae, and comes to the somewhat ambiguous conclusion 
that the hypothesis upon which Frank bases his idea of trans- 
verse heliotropism is incorrect, though, as far as the facts go, 
Frank is on the whole right. With regard to the lamina, 
Vochting considers that the effect of light is to bring it into 
that position in which it receives the maximum of incident 
rays. With regard to the petiole, it is stated to be negatively 
geotropic, positively heliotropic, and persistently epinastic in 
its basal portion. 
Finally, there is an important paper by Krabbe 3 in which 
he arrives at the general conclusion that the light-position of 
leaves cannot be explained by ascribing it to simple combina- 
1 Detmer: Ueb. Photoepinastie der Blatter, Bot. Zeitg. 1882. 
a Vochting : Ueb. die Lichtstellung der Laubblatter. Bot. Zeitg., 1888. 
3 Krabbe : Zur Kenntniss der fixen Lichtlage der Laubblatter. Pringsheim’s 
Jahrb. f. wiss. Bot. XX, Heft 2, 1889. 
