ENVIRONMENT 85 



The wormwood of the desert is more bitter 

 even than the wormwood which grows where 

 there have been fewer enemies. 



The yuccas, the aloes, the euphorbias, all have 

 counterparts in their families, which, needing 

 less protection, show less bitterness, less poison, 

 fewer spines. 



And even rare cactus plants from protected 

 localities, and those of the less edible varieties, 

 give evidence, by the fewness of their spines, that 

 their family struggle has been less intense than 

 the struggle of the cactus which found itself 

 stranded in the bed of a former inland sea. 



Plants which have shown even greater adap- 

 tive powers than the cactus are to be found in 

 the well-known algse family. 



One branch of this family furnishes an apt 

 illustration of the scant nourishment to which a 

 plant may adapt itself. 



Microscopic in size, it lives its life on the upper 

 crust of the Arctic snow storing up enough en- 

 ergy in the summer, when the sun's rays liquefy a 

 thin film of water on the icy surface, to sustain 

 life in a dormant stage during the northern 

 winter's six months of night. 



With nothing but the moisture yielded from 

 the snow, and what nutriment it can gather from 

 the air, this plant, called the red snow plant, 



