April 1, 1920 A Teosinte-Maize Hybrid 7 



The terms "linkage" or "coupling," which are in more general use, might 

 be used in place of coherence; but both these terms imply that the rela- 

 tion is between Mendelian or alternative characters, while most of the 

 characters under discussion show quantitative instead of alternative 

 differences. Furthermore, there appears to be no term in general use 

 that can be applied to the cases where the correlation is the opposite of a 

 linkage or coupling. The use of the word "repulsion" would seriously 

 confuse the issue, since that term implies the disassociation of dominant 

 characters without regard to whether they have entered the hybrid from 

 the same or different parents. In using "coherence" instead of "linkage" 

 there is no intention to imply that the ultimate determinants of the 

 characters are not inherited in Mendelian fashion; but since no attempt 

 toward factorial analysis is made, it seems better to use a more general 



term. 



DESCRIPTION OF CHARACTERS 



Thirty-three characters were recorded and their correlations considered. 

 Many of these characters fall into groups the members of which would 

 seem to be mutually related, either physically of physiologically. Eight 

 such groups are recognized, comprising in all 26 characters. Among the 

 7 remaining characters considered as independent, physiological rela- 

 tions, if they exist, are more obscure. The grouping of the characters 

 is shown below, with the abbreviated designations of the characters which 

 will be used throughout the paper. 



HEIGHT GROUP (P. II-16) 



Height. — Height of the main culm in decimeters. 



Total leaves. — Total number of leaves or nodes produced on the main culm. 



Height op sucker. — Height of the tallest sucker or tiller in decimeters. 



Sucker index. — Height of the tallest sucker, expressed as a percentage of the height 

 of the main culm. 



Circumference index. — Circumference of the thickest intemode in millimeters, ex- 

 pressed as a percentage of the height of the main culm measured in centimeters. 



Nodes without branches. — Number of nodes between the uppermost sucker, or the 

 surface of the grotmd, and the lowest developed branch. 



NODES ABOVE GROUP (P. 1 6-1 9) 



Nodes above. — Number of nodes on the main culm above the ear or uppermost 



branch . 

 Nodes above on third.— Number of nodes above the uppermost secondary branch 



of the third branch from the top. 

 Nodes on third. — Number of nodes on the third primary branch from the top. 



TASSEL GROUP (P. 1 9-2 1 ) 



Primary branches. — Number of primary branches in the terminal inflorescence of 



the main culm. 

 Secondary branches. — Number of secondary branches in the terminal inflorescence 



of the main culm. 

 Secondary index. — Number of secondary branches, expressed as a percentage of the 



primary and secondary branches combined. 

 Tassel branches on third. — Number of branches in the terminal inflorescence of 



the third branch from the top. 



