CHAP.Xm. MANNEE OF OAPTURINa INSECTS. 305 



to reopen after 20 hrs. Lastly another leaf was exposed for 4 m. 

 to only four drops of the ether ; it was rendered insensible, and 

 did not close when its filaments were repeatedly touched, but 

 closed when the end of the open leaf was cut off. This shows 

 either that the internal parts had not been rendered insensible, 

 or that an incision is a more powerful stimulus than repeated 

 touches on the filaments. Whether the larger doses of chloro- 

 form and ether, which caused the leaves to close slowly, 

 acted on the sensitiye filaments or on the leaf itself, I do not 

 know. 



Cyanide of potassium, when left in a bottle, generates prussic 

 or hydrocyanic acid. A leaf was exposed for 1 hr. 35 m. to the 

 vapour thus formed; and the glands became within this time 

 so colourless and shrunken as to be scarcely visible, and I at 

 first thought that they had all dropped off. The leaf was not 

 rendered insensible; for as soon as one of the filaments was 

 touched it closed. It had, however, suffered, for it did not 

 reopen until nearly two days had passed, and was not even 

 then in the least sensitive. After an additional day it recovered 

 its powers, and closed on being touched and subsequently re- 

 opened. Another leaf behaved in nearly the same manner after 

 a shorter exposure to this vapour. 



On the Manner in which Insects are caught. — We will 

 now consider the action of the leaves when insects 

 happen to touch one of the sensitive filaments. This 

 often occurred in my greenhouse, but I do not know 

 whether insects are attracted in any special way by 

 the leaves. They are caught in large numbers by the 

 plant in its native country. As soon as a filament is 

 touched, both lobes close with astonishing quickness ; 

 and as they stand at less than a right angle to each 

 other, they have a good chance of catching any in- 

 truder. The angle between the blade and footstalk 

 does not change when the lobes close. The chief seat 

 of movement is near the midrib, but is not confined 

 to this part; for, as the lobes come together, each 

 curves inwards across its whole breadth ; the marginal 

 spikes however, not becoming curved. This move- 



