ENVIRONMENT 77 



into broad slabs. It lowered its main source of 

 life and sustenance far beneath the surface of 

 the ground and found it possible thus to persist 

 and to prosper. 



Perhaps there were, in the making of the 

 desert, other plants not so adaptable as the 

 cactus, plants which perished and of which man 

 has no knowledge or record. 



And so, we may assume, the cactus and those 

 other plants which adapted themselves to the 

 new conditions crowded out those which were 

 unable to fit themselves to survive under these 

 gradually changing conditions. 



But there came animals to the bed of this one- 

 time sea, attracted, perhaps, by the cactus and 

 its contemporaries, which offered them food of 

 satisfying flavor and easy access. 



Of the plants which had survived the evapora- 

 tion of the sea and the heat of the broiling sun, 

 there were many, quite likely, which failed to 

 survive the new danger — the onslaught of the 

 animals. 



Species by species the vegetation of the desert 

 was thinned out by the elements and by the 

 animals; and the animals, with plant life to feed 

 on, multiplied themselves in ever-increasing 

 hordes, till perhaps the cactus was but one of a 

 hundred plants to survive. 



