90 



The Plant World. 



pear country of the world and its population has obtained a 

 portion of its sustenance from this crop since the earliest tribal 

 times. The Mexicans appreciate and take pride in the spineless 

 forms, and, though ignorant of the laws of plant breeding, have 

 very likely made slight improvements in these plants, whatever 

 advantage they may have gained from time to time being held 

 by vegetative propagation, which is universally practiced. 



It has been assumed by some that the improvements of 

 spineless forms were made in the Mediterranean region of Europe. 



Fig. 5. — Map of the United States, showing the areas (=haded) where "spineless" 

 prickly pears may be grown. The minimum winter temperatures will prevent their 

 growth outeide of the shaded areas. Reproduced by courtesy of the Bureau of 

 Plant Industry. 



This assumption is probably based on the fact that the plants 

 are more numerous there now than elsewhere in the world. It 

 seems doubtful, however, whether this assumption expresses 

 more than a partial truth, for there is an abundance of forms 

 today, scattered all over Mexico, which are just as spineless asany 

 that grow, and apparently they are identical with the Mediter- 

 ranean forms. It is quite possible that the spineless forms were 

 taken to Europe from Mexico and South America in much the 

 same condition as they are grown there today, though importa- 

 tions of spineless forms from Mexico and Southern Europe have 



