LUTHER BURBANK 



cessors developed it only after the evolution of 

 the insect tribe. And we have doubtless been cor- 

 rect in ascribing the ready variability of the floral 

 envelope to the fact of its relative newness. The 

 stalk and branches and leaves of the plant have 

 persisted, more or less modified in form but essen- 

 tially unchanged in functions, from the remotest 

 periods, and hence have attained a fixed and deter- 

 minate arrangement of their hereditary factors 

 that is difficult to disturb. 



The conspicuous advertising sign that we call 

 a flower has been put forth so recently that it has 

 not attained any such degree of stability. 



And in particular, the color of the flower is an 

 endowment that, as contrasted with the general 

 structure of the plant, must be thought of as only 

 a thing of yesterday. We are justified in believ- 

 ing that even among the old tribes of plants — 

 those whose primeval forebears have left their 

 remains in the geological strata — the flower is the 

 one structure that has been most subject to varia- 

 tion. And we may doubt whether there is any 

 flower whatever that has not changed its color 

 more or less within comparatively recent times, 

 geologically speaking. 



Something has been said as to the probable 

 relations of the different primary colors in their 

 various associations in the floral envelope. We 



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