Variation and Correlation of Oats — Part II 



105 



It can be said, from the results here shown, that practically the same 

 correlation coefficients will be obtained when plants are used as- the units 

 of calculations as when the separate culms making up these plants are used 

 as the units, but that there is a uniform tendency for the correlation to be 

 greater when culms are used as the units. Greater differences exist in the 

 correlation when average weight of kernels enters as one of the characters, 

 but none of the differences found are great enough to be of special signifi- 

 cance. The correlation coefficients obtained by the several investigators, 

 therefore, whether they worked with culms or with plants, are comparable, 

 with slight reservation, as far as any effect of this usage is concerned. The 

 same may be said for the means, the standard deviations, and the coeffi- 

 cients of variability. All these constants, however, are generally slightly 

 higher when the separate culms are the units than when the plants are the 



units. 



Biometrical comparison of varieties of oats 



The results obtained by Waldron (1910) in biometrical work with oats 

 differed radically from those obtained by the writer (1911). The cor- 

 relations obtained by Waldron between average weight of grain and number 

 of grains per head, length of culm, and length of head, were of considerable 

 value, amounting to forty to sixty per cent, and were negative. Those ob- 

 tained by the writer for the same characters were large and positive. Some 

 explanation of these discordant results was sought. One suggestion was 

 that the use of different varieties had been the cause. In order to test 

 the theory that correlations may be affected by varietal differences, 

 pure lines of four different varieties were grown side by side under similar 

 conditions during the season of 1911. These pure lines had been grown 

 for several years by the Department of Plant-Breeding in the comparative 

 rod-row tests that it was conducting. Fifteen-gram lots of seed were 

 sown in eighteen-foot rows, and the rows were a foot apart. The varieties 

 used were as follows: 



» Series 



1200 



1219 



1238 



1257 



Variety 



Pure line 



Great American 



Early Champion 



Welcome 



Sixty Day 



125-20 

 137-6 

 123-5 

 62-II-6-3 



