220 THE STORY OF THE PLANTS. 



ing and diffused, so as to go outward towards 

 the point where the water drips on them. 

 Moreover, in this latter case it is found, on 

 digging up the plant carefully, that the ab- 

 sorbent tips of the rootlets are clustered 

 thickest about the exact spots where the leaves 

 habitually drop the water down upon them. 

 Every plant is thus to some extent a catchment- 

 basin which utilises its own rainfall : it collects 

 rain for itself, and conducts it by a definite 

 system of pipes and channels to the precise 

 spots in the soil where it can best be sucked up 

 for the plant's own purposes. 



On the other hand, while every part of every 

 plant is thus minutely arranged for the common 

 advantage, every species of plant and animal 

 fights only for its own hand against all comers. 

 Nature is therefore one vast theatre of plot and 

 counterplot. The parasites prey on the vegeta- 

 tive kinds ; the vegetative kinds respond in turn 

 by developing checks to counteract the parasites. 

 The squirrels produce sharper and ever sharper 

 teeth to gnaw through the nutshells ; the nut- 

 trees retaliate by producing for their part thicker 

 and ever thicker shells to baffle the squirrels. 

 And this play and by-play goes on unceasingly 

 from generation to generation ; because only the 

 cleverest squirrels can ever get enough nuts to 

 live upon ; and only the hardest-shelled and 

 bitterest-rinded nuts can escape the continual 

 assaults of the squirrels. In order, therefore, 

 really to understand the structure and life of 

 any one species, we should have to know in the 

 minutest detail all about its native conditions, 



