[Cir. 132—0 



MOSAIC COHERENCE OF CHARACTERS IN SEEDS OF MAIZE/ 



By G. N. Collins, Botanist, OJ)ice of Crop Acclimatization and Adaptation Investigations. 



In the progeny of crosses between individuals that differ in a 

 number of characters there is often a tendency for the original com- 

 binations of characters to remain together instead of being dis- 

 tributed indiscriminately. This tendency for groups of characters 

 represented in the parents to reappear has been recognized as a 

 factor of heredity and is called "coherence." Hybrids between 

 Egyptian and Upland cotton afford a good example of the coherence 

 of characters. The corolla of Egyptian cotton is tubular in form and 

 yellow in color. The flowers of Upland varieties are white and have 

 a more open, cuplike form. Among hybrids between these two 

 types yellow-flowered plants almost invariably have the flowers 

 tubular and show other Egyptian characters. Yellow flowers that 

 are spreading or white flowers that are tubular are of very rare 

 occurrence.^ There is thus said to be a coherence between the color 

 and form of the corolla and in this instance the coherence is nearly 

 perfect. 



Coherence of characters has usually to be determined by statis- 

 tical methods, it being necessary to examine a large number of hybrid 

 individuals to determine whether certain combinations occur more 

 frequently than the laws of chance would indicate. In hybrids 

 between Chinese maize with waxy endosperm, and our common 

 varieties with horny endosperm there is a definite tendency for the 

 particular combinations of endosperm texture and aleurone color 

 that existed in the parents to persist and reappear in a relatively 

 large percentage of the progeny. This partial coherence of characters 

 has been found without exception in the progeny of the 100 or more 

 crosses that have been examined. 



To demonstrate a coherence of this nature it is necessary to sepa- 

 rate the seeds into the two classes, colored and white. If there is 

 found to be a significant difference between the percentage of waxy 

 seeds in the two groups there is a correlation. If the largest per- 

 centage of waxy seeds is found in the group .having the same aleu- 

 rone color as the waxy parent the correlation is a coherence. 



1 Issued July 19, 1913. 



2 Cook, O. F. Suppressed and intensified characters in cotton hybrids. U. S. Department of Agri 

 culture, Bureau of Plant Industry, Bulletin 147, p. 17, 1909. 



[Cir. 1.32] 19 



