180 



INTBODUCTION TO BOTANY 



171. Principles upon which wheat breeding depends. 1 The 

 work of the earliest breeders of wheat was not based on any 

 general knowledge of the laws of plant variation and inheri- 

 tance. The principles of breeding, as applied to the small 



grains, were first worked out 

 by Professor W. M. Hays 

 of the University of Minne- 

 sota Agricultural Experi- 

 ment Station, and by Dr. 

 Hjalmar Nilsson, director 

 of the experiment station 

 at Svalof, Sweden. Some of 

 the main principles upon 

 which wheat breeding de- 

 pends may be stated as 

 follows : 



1. Every species of cereal 

 usually comprises many 

 well-marked varieties, or, as 

 they are sometimes called, 

 elementary species. Some- 

 times several hundreds of 

 these are included in each 

 of the longest-cultivated spe- 

 cies of grain ; this is notably 

 true in the case of wheat. 



2. The varieties, while 

 still growing in the field, 

 may be distinguished by 

 such botanical characters as 



the position, shape, size, and bearded or beardless condition of 

 the head ; the form, size, and appendages of the spikelets which 

 it contains ; and the size, shape, color, and hardness of the grain. 2 



1 See De Vries, Plant Breeding. The Open Court Publishing Company, 

 Chicago. 



2 The hardness cannot be accurately known until the grain is ripe and dry. 



FIG. 155. A hybrid wheat and the parent 

 forms 



The hybrid is in the middle. It is somewhat 

 intermediate between the parents, being 

 nearly (though not quite) beardless, like the 

 right-hand parent, with a length of head 

 intermediate between the two and with 

 the grains and their covering bracts stout, 

 as in the left-hand parent. Photograph by 

 Minnesota Agricultural Experiment Station 



