180 
INTRODUCTION 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 
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 
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.” 
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. 
