LUTHER BURBANK 



the right stage, you will find that you must pull 

 open the little bracts in which the flowers are 

 encased, in order to make the stamens and pistils 

 visible. Under ordinary circumstances, insects 

 cannot find access to them. The wind has no 

 influence over them. Their normal habit is to 

 fertilize the pistil of each individual flower with 

 pollen from the stamens that grow within the 

 same closed receptacle. 



This is inbreeding of the closest and most 

 intimate character, and there is obviously no 

 ordinary opportunity to introduce the element of 

 variability which, as we have seen illustrated over 

 and over, cross-fertilization brings. 



So the essential qualities that make wheat 

 valuable have been aggregated in a few fixed 

 combinations, and the resulting varieties of wheat, 

 differing not very widely from one another, are 

 never crossed, unless by artificial means to meet 

 the special needs of the plant developer. 



They remain fixed because they are of pure 

 lineage. 



MIXED ANCESTRY AND INBREEDING 



The case of the wheat is typical. Its develop- 

 ment furnishes an illustration of the method 

 through which many specialized races of animals 

 and plants under domestication have been devel- 

 oped. Indeed, it might almost be said that the 



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