TYPE AND VARIABILITY 



449 



SECTION VIII STUDIES IN TYPE AND VARIABILITY 



OF THE SAME VARIETY OF CORN RAISED UNDER 



DIFFERENT CONDITIONS AS TO FERTILITY 



The effect of the conditions of life upon variability, as distinct 

 from mere development of the mass, is well illustrated in the 

 behavior of a single variety of corn (Learning) grown under 

 different conditions as to fertility. This was the crop of 1906 

 upon land that had been in pasture for eighteen years previous 

 to 1895, in a three-year rotation of corn, oats, and clover from 

 that time till the present, with the fertility treatment indicated 

 in the tables (pages 450 and 45 i) since the year 1901. 



Discussion of data. As to weight of ear, it will be noted (see 

 tables, pages 450 and 451) that the mode and mean correspond 

 very closely to yield ; that is, that increased yield is mainly due 

 to heavier ears. This is inevitable from the uniform method of 

 planting with two stalks to the hill. In respect to variability, 

 however, we can detect little difference except in the last plot, 

 which was planted with three stalks to the hill. 



In respect to length and circumference of ear it is noticeable 

 that the higher yields are accompanied by the longer and larger 

 ears for the reasons given above. The most significant fact in 

 the table is that corn is far more variable as to length than 

 as to circumference, but that neither is especially affected by 

 fertility. 



A general correspondence between circumference and number 

 of rows is evident, showing a tendency to constancy as to size 

 of kernel, but again variability is not greatly different for the 

 different yields. So far as this instance can be accepted as a 

 safe criterion, we may deduce the following principles : 



1. That type is directly and largely dependent upon food 

 supply. 



2. That variability is not greatly influenced by specially 

 favorable conditions of life, tending to become less rather than 

 greater as all individuals are afforded ideal opportunities for 

 development. 



