Variation and Correlation of Oats — Part II 87 



units for correlation. The writer (1911) reported data on oats, plants 

 being used as units; but in the same paper some constants worked out 

 by Humbert were quoted, these having been worked out with the culm 

 as the unit of calculation. Atkinson (1912), in some recent and as yet 

 unpublished work, has used the culm as the unit in statistical work with 

 several varieties of wheat. 



It seemed important, therefore, in view of the considerable amount 

 of statistical work being done with the cereals, to make some trial of 

 these methods in order to determine their comparative value. Accord- 

 ingly 300 plants of oats, grown in 1911, three inches apart in rows one 

 foot apart, were chosen for use. These were a pure line (137-6) of the 

 variety Early Champion, which had been grown for several years by the 

 Department of Plant-Breeding at Cornell University. Each culm of 

 each of these 300 plants was measured and recorded separately, the yield 

 and the number of grains produced on each culm being a part of the data 

 taken. There were in all 862 culms produced by the 300 plants, or an 

 average of 2.87+ culms per plant. The numbers of plants, with the 

 different numbers of culms, are as follows: 



Number of culms per plant ... 1 2 3 4 5678 

 Number of plants 41 52 144 39 18 4 1 1 



The constants for the variation and correlation of certain characters 

 of these plants were then determined, the various culms being dealt with 

 as individuals in the one case and the plants being dealt with as indi- 

 viduals in the other; in the latter case, the average per culm of plant being 

 determined. The means and measures of variation determined by the 

 two methods are given in Table 1. Series 1221 is the series worked with, 

 the individual plants here being the units. Series 22 is the designation 

 given to the culms making up the plants of series 1221, when these separate 

 culms are dealt with as units. 



The data in Table 1 will now be considered. The average yield of culm 

 per plant in decigrams has a mean of 7.890 ± .118. The total yield 

 of culm in decigrams has a mean of 8.416 ± .109. The yield of culm is 

 larger by .526 ± .161 decigrams, the difference being only about three 

 times its probable error. Considering standard deviation, it is seen 

 that for the average yield of culm per plant it is 3.034 dz .083, while for 

 the total yield of culm it is 4.728 ± .077. The coefficients of variability 



