ON USEFUL SUBSTANCES IN CACTUS 



canned food, in that their food content remains in 

 perfect condition on the plants year after year 

 until needed. Nothing more is required than to 

 plant the Opuntias, and fence them against the 

 encroachment of animals. It is not necessary to 

 cultivate them, although it is advantageous during 

 the first two or three years, nor need any attention 

 be paid them until their slabs are needed. 



They would thus grow enormously and when 

 the occasion arose they would supply an almost 

 indefinite quantity of food to meet the needs of a 

 population that otherwise must die of starvation. 



The value of a plant that need not be cultivated 

 and needs no preparation yet which will perpetu- 

 ally hold in reserve a colossal quantity of food per 

 acre, constantly adding to it (the annual increase 

 being measured in scores or even in hundreds of 

 tons), offers a refuge to populations that are 

 threatened with years of drought and failure of 

 cereal crops that is not duplicated by any other 

 food produced hitherto under cultivation. 



Even if the new spineless Opuntias had no 

 other function than this, the time and labor 

 devoted to their production would obviously be 

 repaid a million fold. 



IMPORTANT BY-PRODUCTS 



There is one curious property of the slabs of 

 the Opuntias that to some extent militates against 



[249] 



