June 19, 1916 Correlated Characters in Maize Breeding 449 



Owing to the small number of first-generation individuals and the 

 consequent uncertainty that attaches to correlation coefficients in that 

 generation, it is, on the other hand, possible that other correlations 

 shown in the second-generation plants are really genetic. From this 

 point of view, it should be noted, however, that 18 of the second-genera- 

 tion correlations are negative. 



The possibility of a reduction of physiological correlations must also 

 be considered. The existence of a significant positive correlation in the 

 first generation is taken to indicate a physiological correlation between 

 the characters. With such characters as branching space and the number 

 of branches, the relation is obvious; indeed this relation might almost 

 be classed as physical, since as the branching space approaches zero the 

 number of branches must necessarily become less. There would also 

 appear to be a necessary relation between one-sidedness and angle of the 

 tassel axis, for a perfectly erect tassel could scarcely occur with a high 

 degree of one-sidedness. Where correlations of this nature are lowered 

 in the second generation, it would seem necessary to assume that this 

 reduction is brought about by a tendency for the characters from different 

 parents to reappear in the same individual, thus reducing the normal 

 physiological correlation that exists between the characters. 



The following are two such character pairs : 



First Second Differ- D. 



generation generation ence P.E. 

 One-sidedness and low density 



of spikelets o. 36±o. 12 c. c30zto. 059 o. 330±o. 13 2. 5 



Large angle of tassel axis and 



short glumes 47± .10 •C43± .056 •42'j± .114 3.7 



It has been mentioned that with respect to both the number of erect 

 leaf blades and the angle of tassel axis there was a tendency for the plants 

 to fall into two groups. This raised a doubt as to the applicability of the 

 customary "product-moment" method of calculating the correlation 

 coefficient where these characters were involved. This group of correla- 

 tions was therefore recalculated, using Pearson's biserial correlation 

 coefficient (Pearson, 1909). Slightly different values were obtained, but 

 no additional significant correlations were brought to light. 



In the second generation the waxy and homy seed were planted 

 separately, thus affording an opportunity for observing whether the 

 plants from seeds having the waxy endosperm characteristic of the Waxy 

 Chinese variety showed any preponderance of other Chinese characters. 

 No consistent differences were apparent in the general appearance of the 

 rows from the waxy and homy seeds. There was such great individual 

 diversity, however, that comparison was difficult. Analysis of the 

 measurements showed little more. The only character that showed a 

 measurable correlation with endosperm texture was the degree to which 

 tuberculate hairs were developed on the leaf sheaths. 



