No. 550] 



ALEURONE COLORS 



613 



less guarding against foreign pollen and too few to be ac- 

 counted for by any simple monohybrid or dihybrid for- 

 mula. The actual numbers of grains of the various sorts 

 were as follows : 



Ear 1 43 purple, 10 red, 308 white. 



Ear 2 32 purple, 11 red, 222 white. 



Total 75 purple, 21 red, 530 white. 



The fact is familiar that in crosses of purple with 

 white varieties of corn, there often appear in addition to 

 the monohybrid ratio of three purple grains to one white 

 one, purple, red and white grains in the dihybrid ratios 

 of 9:3:4 (East and Hayes 1 and Emerson 2 ). It is also 

 well known that in similar crosses purple and white 

 grains may appear in F 2 in the reversed monohybrid 

 ratio of 1:3 or the dihybrid ratio of 9:7 (East and 

 Hayes 1 ). East 3 has recently shown that for the produc- 

 tion of purple aleurone there must be present three Men- 

 delian factors, C, R, and P, and has demonstrated for 

 purple, red, and white grains the trihybrid ratio of 27 : 9 : 

 28. C is a general color factor, that must be present 

 ordinarily in order that any color may develop, R a fac- 

 tor that has to do with the production of red aleurone 

 when C is present, and P a factor for purple that is ef- 

 fective only in the presence of both C and R. Thus 

 CRP gives purple and CRp red, while all the other 

 possible combinations give white. All this is on the as- 

 sumption that a fourth factor I, an inhibitor of color de- 

 velopment, is absent. Purple color of the aleurone may, 

 therefore, be said to depend upon the presence of three 

 factors and the absence of one, CRPi, red color upon 

 the presence of two factors and the absence of the two 

 others, CRpi, and whites upon the absence of either one 

 of the two factors C or R or upon the presence of a third 

 factor, I, C RP, CrP, or CRPI, etc. 



*E. M. East and H. K. Hayes, Conn. Agr. Expt. Sta., Bui. 167, pp. 57- 

 100,1911. 



2 R. A. Emerson, Amer. Breeders' Assoc., vol. 6, pp. 233-237, 1911. 

 S E. M. East, Amer. Nat., vol. 46, pp. 363-365, 1912. 



