MODE OF REPRODUCTION IN RELATION TO BREEDING 45 



TABLE VII. AVERAGE YIELD PER PLANT OF Fi WHEAT CROSSES AND 



THEIR PARENTS 



crosses are due in a large measure to sterility for there was an 

 appreciably smaller setting of seeds in the crosses than in their 

 parents. 



Crosses between distinct species of self-fertilized plants have 

 been carefully studied in the tobacco genus, Nicotiana. Results 

 obtained may be summed up as follows (East and Hayes, 1912): 



"(a) plants so different that they will not cross; (6) crosses that pro- 

 duce seed that contain no proper embryo ; (c) crosses that produce seed 

 with embryo, but which go no further than the resting stage of the seed; 

 (d) crosses less vigorous than either parent; (e) crosses more vigorous 

 than the average of the parents; and (/) crosses more vigorous than 

 either parent." 



Apparently in wide crosses the normal physiological processes 

 are interfered with. The statement is frequently made that 

 this is due to lack of compatibility between the parents. The 

 specific physiological cause is not yet known. 



EFFECTS OF SELF-FERTILIZATION IN NORMALLY CROSS- 

 FERTILIZED PLANTS 



This subject will be studied in relation to the specific 

 outline for breeding some normally cross-fertilized plants, 

 such as maize and rye. A few data will be presented in 



