306 PINGUICULA VULGARIS. [Cnar. XVI. 
exciting object, must be serviceable in another and probably 
more important way. We have-seen that when large bits 
of meat, or of sponge soaked in the juice of meat, were placed 
on a leaf, the margin was not able to embrace them, but, as 
it became incurved, pushed them very slowly towards the 
middle of the leaf, to a distance from the outside of fully > 1 
of an inch (2°54 mm.), that is, across between one-third and 
one-fourth of the space between the edge and midrib. Any 
object, such as a moderately sized insect, would thus be 
brought slowly into contact with a far larger number of 
glands, inducing much more secretion and absorption, than 
would otherwise have been the case. That this would be 
highly serviceable to the plant, we may infer from the fact 
that Drosera has acquired highly developed powers of move- 
ment, merely for the sake of bringing all its glands Into 
contact with captured insects. So again, after a leaf of 
Dionæa has caught an insect, the slow pressing together of 
the two lobes serves merely to bring the glands on both 
sides into contact with it, causing also the secretion charged 
with animal matter to spread by capillary attraction over 
the whole surface. In the case of Pinguicula, as soon as an 
insect has been pushed for some little distance towards the 
midrib, immediate re-expansion would be beneficial, as the 
margins could not capture fresh prey until they were un- 
folded. The service rendered by this pushing action, as 
well as that from the marginal glands being brought into 
contact for a short time with the upper surfaces of minute 
captured insects, may perhaps account for the peculiar move- 
ments of the leaves: otherwise, we must look at these move- 
ments as a remnant of a more highly developed power for- 
merly possessed by the progenitors of the genus. 
In the four British species, and, as I hear from Prof. Dyer, 
in most or all the species of the genus, the edges of the 
leaves are in some degree naturally and permanently 
incurved. This incurvation serves, as already shown, to 
prevent insects from being washed away by the rain; but it 
likewise serves for another end. When a number of glands 
have been powerfully excited by bits of meat, insects, or any 
other stimulus, the secretion often trickles down the leaf, and 
is caught by the incurved edges, instead of rolling off and 
being lost. As it runs down the channel, fresh glands are 
able to absorb the animal matter held in solution. Moreover, 
the secretion often collects in little pools within the channel, 
