168 LUTHER BURBANK 



apple, for example, will produce but perverted 

 replicas of the original Baldwin if grown in an 

 arid soil, deprived of moisture, and shaded by 

 other trees. Under such conditions, the choicest 

 varieties of apples tend to revert more or less 

 to the primitive type of the wild ancestor of 

 very remote generations. 



Similarly the spineless Opuntia may tend to 

 revert to the wild forms if placed under prime- 

 val conditions. In a stony, arid soil, deprived 

 of moisture, it may not only be stunted in 

 growth, but it may show a propensity to revert 

 to the spiny condition. Such, at any rate, was 

 the case with the earliest spineless opuntias that 

 were produced at Santa Rosa, but this tendency 

 is wholly obviated in the newer ones. 



As the experiment has gone forward, however, 

 the condition of spininess has been more and 

 more subordinated, as just related; the proof 

 being not only that the individual plants are 

 absolutely free from spines and spicules, but that 

 more and more of their seedlings are found to 

 be spineless. And this elimination of the hered- 

 itary factors for spininess is so profound and 

 deep-seated that the newer or more recently de- 

 veloped varieties of spineless opuntias appear to 

 have lost altogether under all circumstances the 

 capacity to revert to the spiny condition. Even 



