LUTHER BURBANK 



of environment, and no one needs to be told that 

 the choicest orchard fruits, for example, will fail 

 signally to justify expectations based on observa- 

 tions of their parent forms, unless they are given 

 proper conditions of soil and cultivation. Gut- 

 tings or buds of the Baldwin apple, for example, 

 will produce but perverted replicas of the original 

 Baldwin if grown in an arid soil, deprived of mois- 

 ture, and shaded by other trees. Under such con- 

 ditions, 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 form if placed under primeval 

 conditions. In a stony, arid soil, deprived of mois- 

 ture, it may not only be stunted in growth, but it 

 may show a propensity to revert to the spiny con- 

 dition. Such, at any rate, was the case with the 

 earliest spineless opuntias that were produced at 

 Santa Rosa. 



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 hereditary factors for spini- 

 ness is so profound and deep-seated that the newer 



[266] 



