156 Transactions of tJie [Sess. 



In 1768 an English naturalist named Ellis sent a drawing of 

 this plant to Linnteus, along with a description of it, in which he 

 suggested that Nature might have a view to furnishing the plant with 

 nourishment in forming the upper joint of its leaf like a machine for 

 catching food. He went on to state that minute red glands dis- 

 charged a sweet liquor, which acted as a lure to insects, which, the 

 moment they touched them with their feet, caused the leaf to close 

 instantly and squeeze them to death ; and that if the insects were 

 strong, three erect spines fixed amongst the glands effectively put an 

 end to their struggles. The movement described by Ellis is substan- 

 tially correct, but he made an error in stating that the glands were 

 sensitive, and that the erect spines played an important part in put- 

 ting an insect to death. His description, however, failed to convince 

 Linneeus that there was anything more in it than a case of extreme 

 sensitiveness. That the sensitiveness resided in the hairs was dis- 

 covered first by an English botanical draughtsman named Edwards, 

 and siibsequently by Dr Curtis, who published an account of it in 

 the 'Boston Journal of Natural History' in 1834; and in the same 

 account Dr Curtis states that the secretion is not a lure, but a true 

 digestive fluid poured out after capture. The hairs are sensitive over 

 their whole surface, so that an insect alighting on the leaf is almost 

 certain to cause it to close. When touched, a motor impulse is con- 

 veyed from the excited hair through the cellular tissue of the leaf- 

 blade to the midrib, the result being that the lobes instantly close. 

 This closing, however, is not at first perfect, the teeth oidy slightly 

 interlacing, so that if the insect be small it is allowed to escape ; but 

 if the insect is large, the glands are induced to secrete and absorb 

 the animal matter, which, according to Darwin, has the effect of 

 causing the lobes to press closely against the body of the insect. The 

 pressure is often so great that the outline of the body of the insect 

 can be seen on the outside of the leaf. These hairs are extremely 

 sensitive to a momentary touch. Darwin found that a piece of 

 human hair 1\ inches long, held dangling over one of them so as 

 to touch it, produced no movement, but a rather thick cotton thread 

 of the same length caused the lobes to close. It would appear, how- 

 ever, that although these hairs are more sensitive to a momentary 

 touch, they are far less sensitive to prolonged pressure than the ten- 

 tacles of Drosera. A piece of human hair ten times the length of 

 that which caused the tentacles of Drosera to bend, when cautiously 

 placed on one of the hairs produced no movement, although in the 

 case of Drosera they were supported by the dense secretion. 



When the lobes are induced to close by mechanically touching the 

 sensitive hairs, they remain closed only a short time ; but when an 

 insect is caught, they remain closed for many days, and Darwin 

 mentions a case where the leaf remained closed for thirty-five days 

 over a large Tipula, On an insect or other animal substance being 



