88 BREEDING CROP PLANTS 



The Howards (1915) state that standing power is due to a 

 combination of a strong root system and stiff straw and report 

 segregation and recombination in a cross between two varieties, 

 each of which contained one character and lacked the other. It 

 was impossible to determine the factors involved. Spillrnan 

 (1909) made a cross between a winter wheat with weak straw and 

 spring wheat with stiff straw and obtained in later generation a 

 winter wheat with stiff straw. Examples of inheritance of other 

 similar characters could be given. It is reasonable to conclude 

 that those growth characters which determine the productive 

 capabilities of each variety are inherited in the same manner 

 as botanical characters. They are due, generally, to the inter- 

 action of numerous factors which are dependent for their full 

 expression on favorable environmental conditions. 



