No. 570] ALFALFA BREEDING 367 



TABLE X 

 Correlation in Pure Races 



form minus correlation existing between them. We thus 

 have two factors both making for yield, but seemingly 

 (probably physiologically) antagonistic to each other. In 

 breeding for high yielding strains we are here again called 

 upon to overcome by selection an antagonistic physiolo- 

 gical correlation. 



This brings us to the following final conclusion which 

 the writer wishes to emphasize : 



In economic plant breeding one frequently encounters 

 physiologically negative correlations such as those, in 

 alfalfa, between height and stooling capacity, height and 

 percentage of leaves, and between yield and quality. In 

 seeking improvement, therefore, the breeder must recog- 

 nize and make use of these facts in the interpretation of 

 results obtained, and also search for races which violate 

 such naturally antagonistic correlations to the greatest 

 possible extent. 



General Conclusions 

 That the complex of allelomorphs, which we call a va- 

 riety, may be definite as both to ultimate composition and 

 organization is not here questioned. When, however, we 

 consider that visible characters are only the expression of 

 the reactions of the vital forces of the plant with the en- 

 vironment, we can realize that the variety, as we see it, is 

 not a definite thing, but is a result of two independent 

 classes of factors. Change either and the result corre- 

 spondingly changes. 



