No. 517] HEAVY AND LIGHT SEED GRAIN 



51 



resented an entire plant. The variety is well defined 

 morphologically, but evidently contains various races or 

 biotypes. 



Among other data secured was the height of culm, the 

 length of head, the number of grains per head and the 

 average weight of kernel. The various measurements 

 were correlated and the results prove very interesting. 



Fig. 1 shows the correlation existing between the aver- 

 age weight of kernel as subject and the number of grains 

 per head as relative. A strong negative correlation is 

 noticed, amounting to very nearly (iO per cent. In other 

 words, the greater the number of grains per head, or, in 

 reality, the larger the head as regards grain, the less the 

 average weight per kernel. 



The mean of the number of grains per head, of the pop- 

 ulation studied, is 22.098 and the mean weight per kernel 

 is 24.913 mg. 



The regression coefficient of the number of grains rela- 

 tive to the average weight of grain is — 1.98. In other 

 words, if we should select grains for planting that weigh, 

 for instance, 30 mg. and above, they would on the whole be 

 selected from heads containing only about 12 or 13 grains, 

 which represent heads considerably below the mean. 

 There would doubtless be an occasional grain from heads 

 above the mean, but such grains would be uncommon and 

 the increasingly larger heads would be more and more 

 sparsely represented in the grain selected for planting. 



Fig. 2 shows the con-elation existing between the aver- 

 age weight of kernel as subject and the length of head as 

 relative. As the number of grains is quite dependent 

 upon the length of head we should expect to find a corre- 

 lation existing between the two, somewhat similar, as is 

 shown in Fig. 1. The actual correlation is negative and 

 amounts to 51 per cent. The mean length of the head is 

 13.583 cm. 



The regression coefficient of the length of the head 

 relative to the average weight of grains is — 0.379. That 

 JS, if we should select grains for planting that weigh, for 

 instance, 30 mg. and above, they would in general be 



