Variation and Correlation of Oats — Part II 213 



with several purposes in view. One purpose has been to determine the 

 averages, the amounts of variation, and the correlations that exist in 

 various characters of oats. Another has been to determine the effects 

 on these characters of various environmental influences. Under the 

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

 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. Webber (1903) has 

 classified correlation into four groups — environmental, morphological, 

 'physiological, and coherital. It is very difficult to place the correlations 

 here considered in this classification. It is certain that no cases of 

 coherital correlations have been shown. Some of the correlations would 

 probably be classed as environmental. But it has been shown that 

 change in environment often produces radical changes in the correlation 

 of certain parts. Environmental correlation, then, is not so simple a thing 

 as might be supposed. Between morphological and physiological cor- 

 relation there is no clear distinction, and it is probable that all the cor- 

 relations here dealt with could be classified under either head. 



The classification given by East (1908) is simpler in its main divisions, 

 these being somatic and gametic, but the subdivisions are not yet distinctly 

 defined. The correlations treated here are somatic, but a further classifi- 

 cation according to the subdivisions given would be difficult and perhaps 

 unprofitable. 



Correlations have been classified by Love and Leighty (1914) as 

 fluctuating and stable, these divisions being based on the behavior of the 

 relationship of the characters concerned when variation occurs in environ- 

 mental conditions, such as exist in different years or in different locations. 

 As the names indicate, the correlations of the first class may be made to 

 vary considerably by changes in conditions, while those of the second 

 class remain of about the same value or are stable in character. Both 

 these classes of correlations are found among those reported in this paper. 



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 Avith 

 oats, practically the same means and correlation coefficients will be obtained 



