ON ENVIRONMENT 
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, and covered the drying 
plains with their verdure. 
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 
dozen plants to survive. 
Then came the fight of the cactus to outdo the 
beasts which sought to devour it—the fight as a 
family, and the fight within the family to see which 
of its individuals should be found fit to persist. 
Of a million cactus plants eaten to the ground 
[17] 
