Cuar. XIII] MANNER OF CAPTURING INSECTS. 249 
that the lobes cannot begin to close, they exert, whilst in 
this position, very little force. 
I thought at first that the gradual pressing together of the 
lobes was caused exclusively by captured insects crawling 
over and repeatedly irritating the sensitive filaments; and 
this view seemed the more probable when I learnt from Dr. 
Burdon Sanderson that whenever the filaments of a closed 
leaf are irritated, the normal electric current is disturbed. 
Nevertheless, such irritation is by no means necessary, for a 
dead insect, or a bit of meat, or of albumen, all act equally 
well; proving that in these cases it is the absorption of 
animal matter which excites the lobes slowly to press close 
together. We have seen that the absorption of an extremely 
small quantity of such matter also causes a fully expanded 
leaf to close slowly ; and this movement is clearly analogous to 
the slow pressing together of the concave lobes. This latter 
action is of high functional importance to the plant, for the 
glands on both sides are thus brought into contact with a 
captured insect, and consequently secrete. The secretion 
with animal matter in solution is then drawn by capillary 
attraction over the whole surface of the leaf, causing all the 
glands to secrete and allowing them to absorb the diffused 
animal matter. The movement, excited by the absorption of 
such matter, though slow, suffices for its final purpose, whilst 
the movement excited by one of the sensitive tilaments being 
touched is rapid, and this is indispensable for the capturing 
of insects. These two movements, excited by two such 
widely different means, are thus both well adapted, like all the 
other functions of the plant, for the purposes which they 
subserve. 
There is another wide difference in the action of leaves 
which enclose objects, such as bits of wood, cork, balls of 
paper, or which have had their filaments merely touched, 
and those which enclose organic bodies yielding soluble 
nitrogenous matter. In the former case the leaves, as we 
have seen, open in under 24 hrs. and are then ready, even 
before being fully expanded, to shut again. But if they 
have closed over nitrogen-yielding bodies, they remain 
closely shut for many days; and after re-expanding are 
torpid, and never act again, or only after a considerable 
interval of time. In four instances, leaves after catching 
insects never re-opened, but began to wither, remaining 
closed—in one case for fifteen days over a fly; in a second, 
