B08 DIONZA MUSCIPULA. Cuap. XIIL 
resist being opened, as by a thin wedge driven 
between them, with astonishing force, and are gene- 
rally ruptured rather than yield. If not ruptured, 
they close again, as Dr. Canby informs me in a letter, 
“with quite a loud flap.” But if the end of a leaf 
is held firmly between the thumb and finger, or by a 
clip, so 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 irri- 
tated, the normal electric current is disturbed. Never- 
theless, 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 diffised 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 
filaments being touched is rapid, and this is indis- 
