CHAP. II. THE EFFECTS OF REPEATED TOUCHES. 35 



cible touch to a considerable number of glands, and 

 not one moved ; but these same glands, after an inter- 

 val of some hours, being touched four or five times 

 with a needle, several of the tentacles soon became 

 inflected. 



The fact of a single touch or even of two or three 

 touches not causing inflection must be of some service 

 to the plant ; as during stormy weather, the glands 

 cannot fail to be occasionally touched by the tall 

 blades of grass, or by other plants growing near ; and 

 it would be a great evil if the tentacles were thus 

 brought into action, for the act of re-expansion takes 

 a considerable time, and until the tentacles are re- 

 expanded they cannot catch prey. On the other 

 hand, extreme sensitiveness to slight pressure is of the 

 highest service to the plant ; for, as we have seen, if 

 the delicate feet of a minute struggling insect press 

 ever so lightly on the surfaces of two or three glands, 

 the tentacles bearing these glands soon curl inwards 

 and carry the insect with them to the centre, causing, 

 after a time, all the circumferential tentacles to 

 embrace it. Nevertheless, the movements of the 

 plant are not perfectly adapted to its requirements; 

 for if a bit of dry moss, peat, or other rubbish, is 

 blown on to the disc, as often happens, the tentacles 

 clasp it in a useless manner. They soon, however, 

 discover their mistake and release such innutritions 

 objects. 



It is also a remarkable fact, that drops of water fall- 

 ing from a height, whether under the form of natural 

 or artificial rain, do not cause the tentacles to move ; 

 yet the drops must strike the glands with considerable 

 force, more especially after the secretion has been all 

 washed away by heavy rain; and this often occurs, 



