424 Vines. — On Epinasty and Hyponasty. 
the experiments, that the epinasty was spontaneous. These 
observations, taken in conjunction with those on the seedlings 
of Cucurhita , seem to prove conclusively the falsity of Detmer’s 
theory of photo-epinasty. 
If any further evidence is required, it is afforded by my 
observations on Primida officinalis , which has proved itself to 
be most instructive. If a plant be taken which has been 
growing fully exposed to light, it will be seen that the older 
radical leaves are more or less nearly horizontal ; those next 
in age, obliquely ascending; and the youngest very nearly, 
but not quite, vertical. On being placed in darkness in the 
normal position, the first change to be noticed is that the 
younger leaves become quite vertical, whilst the older leaves, 
though still growing, remain horizontal. About the fourth 
day in darkness it will be observed that the lamina of the 
youngest leaves is being developed in a revolute manner, 
whilst, at the same time, they curve outwards throughout 
their whole length : at the same time the older, but still 
growing leaves, instead of being horizontal, have become 
arched, their apices being firmly pressed against the soil. 
About this time (sixth day) growth ceases, and the positions 
remain unchanged. 
Exactly the same phenomena are exhibited when the plant, 
instead of being placed in the normal position, is rotated on 
the clinostat. 
The natural interpretation is, that the movement of the 
youngest leaves into line with the long axis of the plant when 
first placed in darkness is due to hyponasty, whilst the subse- 
quent curvature outwards, away from this line, is due to 
epinasty. In other words, the leaves of Primida are hypo- 
nastic at their first development, becoming subsequently 
epinastic, at the time when the expansion of the lamina be- 
gins, and remaining so until growth ceases. 
Somewhat similar results to those recorded of Primula were 
obtained with Vicia Faba. At their first development the long 
axis of the leaf is nearly parallel to that of the stem, the 
lamina of each leaflet being longitudinally infolded ; in other 
