424 MOVEMENTS. 



species of Portulaca, where the stamens, upon contact, move 

 outwards. 



1097. The gynandrous style of Stylidium is curved down- 

 wards ; when it is lightly touched it suddenly flies to the other 

 side of the flower, although sometimes it merely straightens 

 itself. 



Sensitive lobes of the style or stigma are possessed by Mimu- 

 lus and some other Scrophulariaceae, 1 by Martynia, and some 

 allied plants. 



1098. In all the foregoing cases the sensitiveness is greatest 

 when the plants, or their sensitive parts, are kept at a tolerably 

 high temperature. Sachs has shown that the most favorable 

 temperature for Mimosa movements is about 36 or 37 C. 



1099. Effects of anaesthetics upon sensitiveness in plants. When 

 a young plant of Mimosa is placed under a bell-jar in which a 

 sponge wet with chloroform or an equivalent anaesthetic has 

 filled the confined atmosphere with its vapor, some of the leaflets 

 droop and remain so, while others retain their normal position. 

 But after a while the leaflets will be found to have lost all power 

 of reacting to a touch ; in short, they have become insensitive. 

 The same effect is observed in the case of Barberry stamens. 

 Its explanation is looked for in the changed relation of the 

 sensitive cells to water when they are subjected to the influence 

 of an anaesthetic. 



1100. Plants possess no nervous system. That sensitive plants 

 must have nerves, or tbeir equivalent, for the recognition of im- 

 pressions and the transirission of their influence to a somewhat 

 distant point was formerly held by many writers, but this 

 opinion is not now entertained by any physiologist. 2 



See Heckel's Memoir, Coraptes Rendus, Ixxix., 1874, p. 702. 



3 " Finally, it is impossible not to be struck with the resemblance between 

 the foregoing movements of plants and many of the actions performed uncon- 

 sciously by the lower animals. With plants an astonishingly small stimulus 

 suffices ; and even with allied plants one may be highly sensitive to the slight- 

 est continued pressure, and another highly sensitive to a slight momentary 

 touch. The habit of moving at certain periods is inherited both by plants and 

 animals ; and several other points of similitude have been specified. But the 

 most striking resemblance is the localization of their sensitiveness, and the 

 transmission of an influence from the excited part to another, which conse- 

 quently moves. Yet plants do not of course possess nerves or a central ner- 

 vous system ; and we may infer that with animals such structures serve only 

 for the more perfect transmission of impressions, and for the more complete 

 intercommunication of the several parts " (Darwin : Power of Movement in 

 Plants, 1880, p. 571). 



