40 CLIMBING PLANTS [CHAP. 



many generations, the species not only acquires 

 a much greater facility of response, but the 

 resulting structure becomes " improved " ; l and 

 structural changes of much complexity follow ; 

 so that petioles (e.g., of Clematis) become tendrils 

 (e.g. Naravelia) ; and of leaf-blades, the mid- 

 ribs become tendrils as of the pea ; or flowering 

 branches as of the vine and Virginia creeper, and 

 all these structural adaptations are hereditary. 



Of course Darwinians will say all these 

 adaptive structures arose by " spontaneous con- 

 genital variations," without any aid from any 

 direct action of the environments. If so, the 

 burden of proof lies with them, by bringing 

 forward some illustrations either from Nature 

 or experiments. At present they make no pro- 

 posal of doing so. All Mr Reid does is to credit 

 natural selection with the power of accounting 

 for everything ; 2 but ecologists, who do not 

 theorise, prove their statements by vast induc- 

 tions, if experimental verification is impossible ; 

 but so often is it available that the general con- 

 clusion is completely verified. Take e.g., the 

 adhesive pads, we have seen that they are 

 formed by contact only in the American 

 species ; but the Japanese species of Ampelopsis 

 anticipates it in a partially formed manner. 

 Now, could these adhesive pads arise spon- 



1 This, for instance, is seen in the minute pads of Trichosanthes 

 compared with the well developed ones of Ampelopsis (see below). 

 2 Mr Reid calls natural selection a Deus ex Machind ! 



