ON CACTUS AS CATTL£ FOOD 



To any one who knows the prime necessity of 

 a water supply for cattle and horses under ordi- 

 nary conditions of grazing, such statements seem 

 almost incredible. But they are thoroughly 

 authenticated and, indeed, they need excite no sur- 

 prise in the mind of any one who appreciates the 

 succulent quality of the cactus slab. 



In point of fact, the entire cactus plant is a 

 receptacle for holding water. 



It was doubtless because the leaves of the 

 cactus transpired water, as do all leaves, that these 

 appendages were given up, so that the cactus of 

 to-day is a leafless plant. A plant that grows in 

 the desert finds it necessary to conserve water. 

 So through natural selection the cactus developed 

 the custom of dropping its leaves when they were 

 only tiny bracts, at the very earliest stage of its 

 growth, developing chlorophyll bodies in its slabs 

 to perform the functions usually performed in the 

 leaf of the plant. 



These present a relatively small surface to the 

 air in proportion to their bulk, and conserve in 

 large measure the water that would be transpired 

 from an ordinary leaf system. 



This, combined with the habit of the cactus of 

 sending its long, slender roots deep into the soil, 

 accounts for the power of the plant to grow in arid 

 places. 



[223] 



