CEREAL IMPROVEMENT HYBRIDIZATION 207 



The possibilities of improvement through hybridization, 

 accompanied by discriminating selection, in the hands of 

 skillful breeders, seem to be practically unlimited. 



215. Manner of natural pollination. Under the dis- 

 cussion of each cereal separately, its flowers have been 

 described. It may be stated further that the flowers 

 are anemophilous. It is a fact of much importance in 

 connection with breeding operations that all small cereals 

 except rye are generally self-pollinated. The degree of 

 closeness of fertilization of wheat, oats, and barley ap- 

 pears to increase in about the order named, barley being 

 extremely exclusive. In fact, the development of the 

 barley plant, and particularly the relation of time of 

 flowering to that of emergence of the spike, are such that 

 natural cross-fertilization is, in many instances, probably 

 impossible, and even artificial crossing of certain groups 

 is accomplished with difficulty. It is no doubt partly for 

 these reasons that there are a greater number of estab- 

 lished varieties of these cereals than there are of rye, as 

 varietal distinctions in the former are not constantly 

 obliterated by natural crossing. However, the number of 

 varieties probably depends largely also on the number of 

 foundation species of the cereal and its age in cultivation. 



216. Pollination of rye. That the rye flower is usually 

 self-sterile there seems little doubt (see Ulrich, 1902). 

 However, a single spike of rye when isolated may pro- 

 duce a few kernels ; l and several spikes of the same plant, 

 inclosed with each other, but isolated from others, may 

 produce a still larger number of kernels. There is ap- 

 parently a varietal difference in this regard, some varieties 

 producing a larger number than others, although none 



1 A spike is occasionally found which sets a large number of 

 seeds, but this may be due to accidental crossing. 



