ON THE WINGS OF THE WIND. 43 



Why is this ? Why isn't the plant content just to let 

 its grains or berries drop quietly on to the soil beneath, 

 and there shift for themselves as best they may on their 

 own resources ? 



The answer is a more profound jpne than you would at 

 first imagine. Plants discovered the grand principle of 

 the rotation of crops long before man did. The farmer 

 now knows that if he sows wheat or turnips too many 

 years running on the same plot, he ' exhausts the soil,' 

 as we say deprives it of certain special mineral or 

 animal constituents needful for that particular crop, 

 and makes the growth of the plant, therefore, feeble or 

 even impossible. To avoid this misfortune, he lets the 

 land lie fallow, or varies his crops from year to year 

 according to a regular and deliberate cycle. Well, 

 natural selection forced the same discovery upon the 

 plants themselves long before the farmer had dreamed 

 of its existence. For plants, being, in the strictest sense, 

 'rooted to the spot,' absolutely require that all their 

 needs should be supplied quite locally. Hence, from 

 the very beginning, those plants which scattered their 

 seeds widest throve the best ; while those which merely 

 dropped them on the ground under their own shadow, 

 and on soil exhausted by their own previous demands 

 upon it, fared ill in the struggle for life against their 

 more discursive competitors. The result has been that 

 in the long run few species have survived, except those 

 which in one way or another arranged beforehand for 

 the dispersal of their seeds and fruits over fresh and 

 unoccupied areas of plain or hillside. 



I don't, of course, by any means intend to assert that 



