364 



THE AMERICAN NATURALIST [Vol. XLVIII 



Correlations 



In the improvement of varieties of plants, quality is 

 often as important as quantity of yield. This is especially 

 trne in a forage crop, such as alfalfa. Since nitrogen, next 

 to fat, is the most expensive of the necessary food constit- 

 uents, it may be taken as the measure of quality. Com- 

 merical buyers judge alfalfa hay by its purity, odor, color 

 and percentage of leaves retained in curing and baling. 

 The value of the leaves lies in their relatively high nitro- 

 gen content and the consequent increased food value which 

 they impart to the hay. Expressed quantitatively, the cor- 

 relations between the nitrogen content of the hay and the 

 percentage of leaves for the six cuttings were as follows : 



TABLE IV 



Correlation between Nitrogen Content op Hay and Per Cent, of Leaves 



Correlation + .4?± .08 + .6?± .06 + .72± .05 



Correlation + .68± .05 + .61 ± .06 + .52 ± .07. 



That the final value of the hay is markedly dependent upon 

 the composition as well as the percentage of leaves is 

 shown by the following high and fairly uniform correla- 

 tion between the nitrogen content of the hay and the nitro- 

 gen content of the leaves : 



Correlation between Nitrogen Content of Hay and Nitrogen Content 

 of Leaves 



Correlation + .69 ± .05 + .73 ± .05 + .42 ± .08 



Correlation + .67 ± .06 + .85 ± .03 + .74 ± .05. 



If, now, we have shown that the quality of the hay de- 

 pends primarily upon the percentage and composition of 

 the leaves, we may proceed to investigate those factors 

 which indirectly modify the feeding value by influencing 

 the amount or character of these organs. 



The factors most profoundly affecting the percentage 

 of leaves were yield, height and stage of maturity at 

 which the cutting was made. Local or varietal forces were 



