86 Clyde E. Leighty 



ence is significant. In fact a difference of ten times its probable error 

 is certainly significant in so far as there is certainty in human affairs." 

 This method of determining the error of the difference of statistical 

 results compared has been used in the present paper. 



STUDIES TAKEX UP 



The following studies have been taken up and are separately con- 

 sidered hereinafter : 



1. Comparison of biometrical constants determined for oat plants 

 and for the culms of the same plants. 



2. Biometrical comparison of varieties of oats. 



3. Comparison of biometrical constants determined for oat plants 

 grown in hills and in drills. 



4. Effect of different degrees of crowding on biometrical constants 

 of oats. 



The correlation tables for each division are included in the text in 

 proximity to the discussion of the constants determined for each table, 

 except in cases when the same series enters into more than one division. 



Comparison of biometrical constants determined for oat plants and for the 



culms of the same plants 



In taking up variation and correlation studies with the cereals, the 

 question arises as to whether the plants should be considered as units 

 or whether the individual culms of the plants may be considered as the 

 units with which to work. If plants are used as units, averages per culm 

 of plant must be dealt with in many instances. If culms are the units, 

 the actual culm measm-ements are dealt with directly. The feeling may 

 often arise in such work that the measures of variation and correlation 

 may differ somewhat, or even essential^, according to the method used. 



Investigators have made use of one or the other method, or both, 

 rather indiscriminate^. Waldron (1910) has used culms as units in 

 studies with oats, although practically ey&cy cuLm used by him was the 

 entire plant, due to the conditions under which the oats were grown. 

 Roberts (1911) dealt with culms of wheat as units for the crop of one 

 year, and with plants as units for the crop of the succeeding j^ear. 

 ]\Iyers (1911) reported correlations for wheat, plants being used as the 



