192 BREEDING CROP PLANTS 



Studies of the linkage relations of these chlorophyll factors 

 have been made. The seedling factors w and v, and v and I 

 show independent inheritance. The factors which influence the 

 chlorophyll development in the mature plant, g and st, g and 

 j, g and /, j and st, j and /, appear to be inherited independently. 

 Also st and v are inherited independently. 



The linkage relations suggest that one pair of chromosomes 

 in maize contains the factor pairs Gg and LI as well as the aleurone 

 factors, Rr. The japonica striping is influenced by the aleurone 

 factor R, as the presence of R represses striping, while r allows 

 full expression of the pattern. These abnormalities have been 

 discussed in some detail as they show typical Mendelian in- 

 heritance of chlorophyll characters and have considerable 

 bearing on the improvement of corn by the isolation of pure 

 biotypes. 



Some Seed and Ear Characters. Crosses between dents and 

 flints were studied by East and Hayes (1911). There is no 

 immediate visible effect of foreign pollen on the endosperm seed 

 characters which separate these subspecies. Segregation occurred 

 in F 2 ; some forms were obtained in F 3 which bred true to flint 

 habit; some bred true to the dent type; while still others 

 showed segregation. Two or more factors were necessary to 

 explain results. The inheritance of the pointed condition of 

 the seed which is characteristic of white rice pop was also studied 

 by Hayes and East (1915). It was found possible to transfer 

 this pointed condition to the dent subspecies. Results were 

 complex and indicated that two or more cumulative factors 

 were involved. 



Size Characters. Emerson and East (1913) summarized 

 inheritance of size characters of seeds and ears. Weight of 

 seed, seed measurement, number. of rows, and length and diame- 

 ter of ear were characters studied. In general, the FI condition 

 was intermediate, and complex segregation occurred in F^. 

 The inheritance of height of plant, of period of maturity, and of 

 suckering habit, was also studied. The fact that a considerable 

 series of fairly stable varieties is known which exhibit numerous 

 conditions of the development of particular size characters, is also 

 evidence of a complex inheritance. Segregation occurred in 

 F 2 and extracted forms were obtained which approached the 

 original parental conditions. Intermediates, as well as extremes, 

 sometimes bred true. 



