I.KSSO.V 27.] MOVKMI-.NTS. 17! 



light ; this is especially the case with those that cling to walls or 

 trunks by sucker-like disks, as Virginia Creeper, p. 38, fig. G2. 

 When an active tendril comes into contact with a stem or any such 

 extraneous body, it iiu'iirvcs at the; point of coiitiut, and so lays hold 

 of the support : tiu; same contraciion or tendency to curve affecting 

 the whole length of the tendril, it soon shortens into a coil, part coil- 

 ing one way, part the other, thus drawing the shoot up to the sup- 

 porting body; or, if the tendril be free, it winds up in a simple coil. 

 This movement of tendrils is so prompt in the Star-Cucumber (Sic- 

 yos) in Echinoeystis, and in two sorts of Passion-fiowcr, that the 

 end, after a gentle rubhing, coils up by a movement rapid enough to 

 be readily seen. In plants that climb by their leaf-stalks, such as 

 Maurandia and TropaMduui, the movements are similar, but much 

 too slow to be seen. 



491. The so-called sleep of plants is a change of position as night 

 draws on, and in different ways, according to the species, — the 

 Locust and Wood-Sorrel turning down their leaflets, the Honey 

 Locust raising them upright, the Sensitive Plant turning them for- 

 wards one over another ; and the next morning they resume their 

 diurnal position. One fact, among others, showing that the changes 

 arc not caused by the light, but by some power in the plant itself, is 

 this. The leaves of the Sensitive Plant close long before sunset; 

 but they expand again before sunrise, under much less light than 

 thoy had when they closed. In several plants the leaves take the 

 nocturnal position when brushed or jarred, — in the common Sensi- 

 tive Plant very suddenly, in other sorts less quickly, in the Honey 

 Locust a little too slowly for us to see the motion. The way in 

 which blossoms open and close, some when the light increases, some 

 when it diminishes, illustrates the same thing. The stamens of th.e 

 Barberry, when touched at the base on the inner side, — as by an 

 insect seeking for honey, or by the point of a pin, — make a sudden 

 jerk forward, and in the process commonly throw some pollea 

 upon the stigma, which stands a little above their reach. 



*r.l2. In many ol' tlif.-c cisc^; we pl.iinly perceive that a useful end 

 is subserved. Hut what shall wc say of the Vtiuis's I-'ly-trap uf 

 Korth Carolina, growing where it might be sure of all the food a 

 plant can need, yet provided with an apparatus fin* catching insects, 

 and actually capturing thein exi)erily by a sudden motion, in the 

 manner already described (120, Kig. ,S1) ? Or of the leallets of the 



