LINKAGE IN MAIZE: ALEUEONE AND CHLORO- 

 PHYLL FACTORS^ 



E. W. LIXDSTROM 



Genetic linkages or correlations are beginning to con- 

 firm the modern chromosome conception of heredity. As 

 the Mendelian analysis of a species reaches a point where 

 the known genetic factors exceed the number of chromo- 

 some pairs, certain group relations between the factors 

 should become evident. Comparatively few genetic link- 

 ages have been observed in plants, however, probably be- 

 cause the number of Mendelian factors that have been 

 determined is relatively small compared with the number 

 of chromosomes in most species. 



Physiological or morphological correlations, on the 

 other hand, are far more common. But in the present 

 state of knowledge they are not classified as genetic and 

 consequently can not be used as material for determining 

 the relationship between any series of heritable factors. 



An intensive, Mendelian study of maize is gradually 

 revealing genetic correlations. Although more than thirty 

 definite Mendelian factors have now been determined in 

 this species, linkages are limited in number because of 

 the relatively large number of chromosomes (at least nine 

 pairs). 



As early as 1906, Webl)er noted a general correlation 

 in maize between color in the aleurone layer and in the 

 stamens, glumes and silks. At that time, the genetic con- 

 stitution of color in the kernels and other parts of the 

 plant was unknown. Consequently the correlation was 

 not analyzed on a factorial basis. 



In 1911, Emerson described an apparent linkage be- 

 tween color of cob, ])oripan\ Ini^ks, silks, and anthers in 



