248 DIONuEA MUSCIPULA. [Ceap. XIII. 



Cyanide of potassium, when left in a bottle, generates prussie or 

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

 pour thus forme<l; and the glands became within this time so col- 

 ourless and shrunken as to be scarcely visible, and I at first 

 thought that they hud 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 be- 

 ing 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 at- 

 tracted 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 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 intruder. 

 The angle between the blade and footstalk does not change 

 when the lobes close. The chief seat of movement is near 

 the midrib, but it 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 movement of the whole lobe was well seen in 

 a leaf to which a large fly had been given, and from which a 

 large portion had been cut off the end of one lobe; so that 

 the opposite lobe, meeting with no resistance in this part, 

 went on curving inwards much beyond the medial line. The 

 whole of the lobe, from which a portion had been cut, was 

 afterwards removed, and the opposite lobe now curled com- 

 pletely over, passing through an angle of from 120 to 130, 

 80 as to occupy a position almost at right angles to that 

 which it would have held had the opposite lobe been present. 



From the curving inwards of the two lobes, as they move 

 towards each other, the straight marginal spikes intercross 

 by their tips at first, and ultimately by their bases. The 

 leaf is then completely shut and encloses a shallow cavity. 

 If it has been made to shut merely by one of the sensitive 



" [Munk (Rolchert nnd Du ment occnrs nt the c<lKe of the 

 Bolii-UpymoiHl'H ' Arrhlv.' 187(1, lonf. by which the teeth are car- 

 p. 108) states that a special move- rled Inwards. F. D.J 



