FIELD CROPS. 737 



produced, rather thau by docrease in their size. A'ariability decreases with 

 decrease in the means. 



" Correlations are more or less responsive to environmental conditions, and 

 may be divided into fluctuating and stable, according to their behavior under 

 differing environments. There are high, positive, and fairly stable correla- 

 tions between average height of plant and (a) total and average yield, (b) 

 total and average number of kernels produced, (c) average number of spikelets 

 per culm; the correlations between average height of plant and (d) average 

 weight of kernels, (e) number of culms, are fluctuating, being high or low on 

 occasion. There are high, positive, and stable correlations between total yield 

 and (a) culm yield, (b) total ;uid average kernel production, (c) spikelet 

 production, (d) culm production. 



" The average kernel weight is not correlateil closely and consistently with 

 any other character here cousidere<l, except average culm yield, with which the 

 correlation is fairly high and fairly consistent. The average number of spike- 

 lets per culm per plant is correlated (a) fairly highly with the average number 

 of kernels per spikelet; (b) apparently very highly with number of kernels 

 per culm; (c) very highly and stably with average height of i)laut and total 

 yield; and (d) in a fluctuating manner with kernel weight. The correlations 

 between number of culms i)er plant and (a) height, (b) culm yield, (c) number 

 of kernels, are fluctuating, varying greatly from high to low; between number 

 of culms per plant and (d) total yield they are high, positive, and stable; 

 between number of culms per plant and (e) average kernel weight they are 

 fairly stable and always low." 



A bibliograi)hy of cited literature is appended. 



Variation and correlation of oats (Avena sativa). — II, Effect of differences 

 in environment, varieties, and methods on bionietrical constants, C. E. 

 LEKiiiTY (Xew York Cornell Sta. Mem. Jf {1914), PP- 11-216). — The characters 

 of oats dealt with in these studies are height of ciUm and average height of 

 plant, average length of head per plant, total weight of plant, total weight of 

 culm, average weight of culm per plant, number of kernels, number of spike- 

 lets, number of kernels per spikelet of plant, total weight of straw for the 

 entire plant, total weight of straw per culm, average weight of straw jier culm 

 of plant, average weight of kernels per plant, diameter of straw, breaking 

 strength of straw, total yield of plant and culm, and average yield of culm 

 per plant. 



" The study has been pursued with several purposes in view. One punwse 

 has been to determine the averages, the amounts of variation, and the correla- 

 tions that exist in various characters of oats. Another has been to determine 

 effects on these characters of various environmental influences. X'nder the 

 latter head data on the question of methods to be pursued in bionietrical work 

 with cereals have been adduced. Correlation has been carefully considered. 

 This was deemed advisable because of the increasing use of. and attention given 

 to. such studies. The correlations taken up have been principally of yield 

 and average weight of kernels with various other characters. . . . 



" The first division of this study is a comparison of biometrical constants 

 determined for oat plants and for the culms of the same plants. From the 

 results obtained it may be concluded that, for statistical work with oats, 

 practically the same means and correlation coefficients will be obtained whether 

 plants are used as units or the culms of the same plants are used as units, but 

 that these constants will be slightly greater for the latter method. The stand- 

 ard deviations and coefficients of variability will also be greater when culms 

 are the units. The biometrical results obtained by the several investigators. 



