234 MISGELLANEOUIS OBJECTIONS TO THE 



authority of Ilofmeister, 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 tliat the foot-stalks and tendrils are sensitive. 



It is scarcely possible that the above slight movements, 

 due to a touch or shake, in the 3'Oung and growing organs 

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

 But plants i^ossess, in obedience to various stimuli, powers 

 of movement^ which are of manifest importance to them; 

 for instance, toward 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 

 a?iimal 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 in- 

 cidental 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 adrantage of and increased through natural 

 selection. It is, however, probable, from reasons which I 

 have assigned in my memoir, that this wdll have occurred 

 only with plants which had already acquired the power 

 of revolving, and had thus become twiners. 



I have already endeavored to explain how plants became 

 twiners, namely, by the increase of a tendency to slight 

 and irregular revolving movements, which were at first of 

 no use to them; this movement, as well as that due to a 

 touch or shake, being the incidental result of the power of 

 moving, gained for other and beneficial purposes. Whether, 

 during the gradual development of climbing plants, nat- 

 ural selection has been aided by the inherited effects of 

 use, I will not pretend to decide; but we know that certain 

 periodical movements, for instance the so-called sleep of 

 plants, are governed by habit. 



I have now considered enough, perhaps more than 

 enough, of the cases, selected with care by a skillful natu- 

 ralist, to prove that natural selection is incompetent to ac- 

 count for the incipient stages of useful structures; and I 



