LUTHER BURBANK 



awe, if he allows himself to reflect on the mys- 

 terious processes that have taken place within its 

 structure. 



THE ELEMENTS OF VARIATION 



From the present standpoint, however, we are 

 not so much concerned with the mysteries of plant 

 chemistry as with the extremely practical fact 

 that the new sugar prune developed in my orchard 

 has the fixed habit of setting its sugar-making 

 laboratory in operation several weeks earlier than 

 had been the custom with the ancestral races of 

 prunes. 



This interesting and important change of habit 

 had been brought about, as the reader who has 

 perused the earlier chapters will surmise, by a 

 process of selecting, generation after generation, 

 the individual prunes that manifested a tendency 

 to early fruiting. But here as elsewhere we are 

 confronted with the question as to how it was 

 possible thus to change so markedly the habits of 

 a plant within a few generations. 



The answer carries us back in imagination, 

 along lines we have followed in studying other 

 plant histories, to the remote ancestors of the 

 sugar prune. 



We are led to reflect that the time of fruiting 

 of a given plant is largely dependent upon the 

 climate in which the plant habitually grows. Now 



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