808 MISCELLANEOUS OBJECTIONS TO THE [Chap. VII. 



Morren found in several species of Oxalis that the leaves 

 and their foot-stalks moved, especially after exposure to 

 a hot sun. when they were gently and repeatedly touched, 

 or when the plant was shaken. I repeated these obser- 

 vations on some other species of Oxalis with the same 

 result ; in some of them the movement was distinct, but 

 was best seen in the young leaves ; in others it was 

 extremely slight. It is a more important fact that 

 according to the hicrh authoritv of Hofmeister, the young 

 shoots and leaves of all plants move after being shaken ; 

 and with climbing plants it is, as we know, only during 

 the early stages of growth that the foe-stalks and tendrils 

 are sensitiA~e. 



It is scarcely possible that the above slight movements, 

 due to a touch or shake, in the young and growing organs 

 of plants, can be of any functional importance to them. 

 But plants possess, in obedience to various stimuli, 

 powers of movement, which are of manifest importance 

 to them ; for instance, towards and more rarely from the 

 light, — in opposition to, and more rarely in the direction 

 of, the attraction of gravity. "When the nerves and 

 muscles of an animal are excited by galvanism or by the 

 absorption of strychnine, the consequent movements may 

 be called an incidental result, for the nerves and muscles 

 have not been rendered specially sensitive to these stimuli. 

 So with plants it appears that, from having the power 

 of movement in obedience to certain stimuli, they are 

 excited in an incidental manner by a touch, or by being 

 shaken. Hence there is no great difficulty in admitting 

 that in the case of leaf-climbers and tendril-bearers, it is 

 this tendency which has been taken advautage of and 

 increased through natural selection. It is, however, pro- 

 bable, from reasons which I have assigned in my memoir, 



