A DESERT FRUIT. 59 



coming woody in texture and losing their articulated 

 leaf-like appearance. 



Everything on this earth can best be understood by 

 investigating the history of its origin and development, 

 and in order to understand this curious reversal of the 

 ordinary rule in the cactus tribe we must look at the 

 circumstances under which the race was evolved in the 

 howling waste of American deserts. (All deserts have a 

 prescriptive right to howl, and I wouldn't for worlds 

 deprive them of the privilege.) Some familiar analogies 

 will help us to see the utility of this arrangement. 

 Everybody knows our common English stone-crops or 

 if he doesn't he ought to, for they are pretty and 

 ubiquitous. Now stone-crops grow for the most part in 

 chinks of the rock or thirsty sandy soil; they are 

 essentially plants of very dry positions. Hence they 

 have thick and succulent little stems and leaves, which 

 merge into one another by imperceptible gradations. All 

 parts of the plant alike are stumpy, green, and cylindrical. 

 If you squash them with your finger and thumb you find 

 that though the outer skin or epidermis is thick and 

 firm, the inside is sticky, moist, and jelly-like. The 

 reason for all this is plain ; the stone-crops drink greedily 

 by their roots whenever they get a chance, and store up 

 the water so obtained to keep them from withering 

 under the hot and pitiless sun that beats down upon 

 them for hours in the baked clefts of their granite matrix. 

 It's the camel trick over again. So leaves and stem 

 grow thick and round and juicy within; but outside they 

 are enclosed in a stout layer of epidermis, which con- 

 sists of empty glassy cells, and which can be peeled off 



