I 



Variation and Correlation of Oats — Part II 89 



culms are considered as units than when plants are considered as 

 units, and that variability is greater by a large amount in the former 

 case. 



The mean for average number of kernels per culm of plant is less by 

 2.883 ± .986 than is that for number of kernels per culm. The standard 

 deviation in the former case is less by 9.554 ± .696, and the coefficient 

 of variability is less by 14.72 db 1.43. These figures indicate that the 

 average for number of kernels is slightly less, and the variability very 

 much less, when plants are considered as the units of measurement. 



The mean for average number of spikelets per culm of plant is less 

 by 1.552 ± .518 than is that for number of spikelets per culm. The 

 standard deviation in the former case is less by 4.604 ± .366, and the 

 coefficient of variability is less by 12.45 dz 1.29. These figures indicate 

 that the average for number of spikelets is very slightly less, and the 

 variability very much less, when plants are used as the units of 

 measurement. 



The mean for average weight of straw per culm of plant is less by 

 .591 ± .169 than is that for weight of straw per culm. The standard 

 deviation in the former case is less by 1.414 ± .119, and the coefficient 

 of variability is less by 11.33 ± 1.30. These figures indicate that the 

 average for weight of straw is less by a slight amount, and varia- 

 bility is less by a large amount, when plants are used as the units of 

 measurement. 



The mean of average weight of kernels per plant in milligrams is 

 14.080 ± .066. The mean of weight of kernels per culm is 13.851 ± .058. 

 The weight of kernels per plant in milligrams is greater by .229 ± .088 

 milligrams, which is less than three times the probable error. The stand- 

 ard deviation for average weight of kernels per plant is 1.684 i .046, 

 for average weight of kernels per culm 2.540 ± .041. The coefficients 

 of variability are, respectively, 11.96 ± .33 and 18.34 ± .31. These 

 figures denoting variability are greater for the kernels per culm than for 

 the kernels per plant, coinciding in this with the figures for all other 

 characters here considered; but the values of the means are reversed, 

 being here, in the only instance, higher for a character when plants are 

 used as the units of measurement. 



The means here determined are remarkably close together in value. 

 With one exception, however — this being for average weight of kernels — 



