JAN. 4, 1921 kempton: linkage in maiZE 19 



In the first generation the plants showed a segregation with 

 respect to cob color, half the plants having red, the other half 

 white cobs, indicating that the red-cobbed parent was hetero- 

 zygous for cob color. Four self -pollinated ears with red cobs 

 were obtained and progenies of these had approximately three 

 plants with red cobs to one with white. These four progenies 

 are fairly uniform with respect to the Mendelian ratios. The 

 distribution of the plants with respect to cob color and culm 

 characteristics is shown in table 3. The percentage of "cross- 

 overs" varies from 29.6 to 48.8 with an average for the group of 

 38.1. This percentage, though somewhat larger than in the other 

 two hybrids, does not vary from them by an amount too large to 

 be ascribed to chance. 



It may be concluded, therefore, that the genes for cob color 

 and stature are located in the same chromosome and rather 

 widely separated, the distance being between 31 and 43 units. 



The nine second-generation progenies of the liguleless X 

 brachytic cross afford also an opportunity to measure the inter- 

 relations of the leaf and culm characters. These nine progenies 

 vary in the degree of relationship between the brachytic stature 

 and the liguleless leaf. In all but one progeny the correlations 

 were between normal stature and liguleless leaf which is the paren- 

 tal combination. The classes of plants are shown in table 4. In 

 the one exception the probable error does not preclude placing 

 it with the others since the deviation from the mean of the group 

 is but 2.5 times the error. 



The correlation of 0.204 ± 0.049 ^or the entire group indicates 

 a rather loose linkage, the percentage of crossovers being 43.7. 

 The deviation from independence or 50 per cent crossing over is 

 slightly over 4 times the error. It would seem, therefore, that 

 if the genes for these characters are located on the same chromo- 

 some they are widely separated. 



If it is held that the genes for the brachytic and liguleless char- 

 acters are located in the same chromosome 44 units apart it 

 then follows from the relation of brachytic culms to cob color 

 that the gene for liguleless leaves must be either 8 or 80 units 

 from that for cob color. The classes of plants are shown in 



