LIFE HISTORIES OF FAMILIAR PLANTS 



difficult to move upon, let alone feed upon, while 

 the whole arrangement is artfully contrived to 

 conduct it towards the juicy end of this group of 

 leaflets, which are now pointed towards the ground. 

 However, when the caterpillar reaches this part, 

 on which it would naturall}^ begin its meal, 

 the difficulties of feeding there, and the greater 

 difficulty of climbing back up the slopingly- 

 arranged leaflets, usuall}^ result in it dropping 

 to the ground — probably more or less disgusted 

 with sensitive plants and their absurd arrange- 

 ments. Even should it hold to the stem of one 

 plant and endeavour to feed upon the leaves of 

 another, it is equally beaten, for the leaf it touches 

 immediately shrinks from it and drops out of its 

 reach. 



It is clear, I think, that the sensitive plant, like 

 the ^^ woolly bear " and the hedgehog, gains some 

 considerable protection in its struggle for existence 

 by its sensitiveness. However, there is another 

 question that arises when we consider the quaint 

 movements of these plants. How did they first 

 acquire these highl5^-evolved tactics which they 

 now exercise with such conspicuous success against 

 their natural foes ? There must, of course, have 

 been a beginning and then a gradual perfecting of 

 the delicate sensitiveness they now exhibit. Ap- 

 parently a difficult problem is presented when we 

 seek to discover how this habit of shrinking from 

 animal attacks was first acquired. 



Before dealing with this point, however, I 

 would ask my reader to glance at Fig. 49 (Plate ^2). 



62 



