60 LUTHER BURBANK 



correlation of parts. The more conspicuous 

 illustrations of this are obvious to the most casual 

 observer various adaptations of form of tree 

 and shrub and vine to their natural surroundings 

 are so patent that they cannot escape attention. 



But of course the plant experimenter must 

 deal with correlations of a very delicate order. 

 He is called upon to make nice distinctions be- 

 tween individual seedlings of the same variety. 

 All will have the same general formation of stem 

 and leaf. He must look, then, for details of vari- 

 ation that would altogether escape the notice of 

 the untrained observer. But that such differ- 

 ences exist, and that they are signs that to the 

 practiced eye are of the utmost importance, any 

 successful plant experimenter can testify. 



It would obviously be futile to attempt a 

 detailed description of the nice shades of dis- 

 tinction between various seedlings of the same 

 race upon which the plant experimenter depends 

 in forming his selective judgments. That, 

 clearly, must be matter for practical observation. 

 It can be learned nowhere but in the field. But 

 perhaps two or three illustrations may be given 

 that will at least serve in a general way to sug- 

 gest what manner of traits are taken into con- 

 sideration in choosing the individuals with which 

 he is to continue his experiment. 



