THE NATURE AND EXPRESSION OF MENDELIAN FACTORS 139 
stead of displaying complete dominance for any one member of the 
factor system as Shull found for the triangular capsule factors in Bursa, 
the factors here have a certain effect in color production which is additive, 
RrSsTt 
RrSsTt 
RrSsTt 
RrSsTt 
RrSsTt 
rrSsTt RrSsTt RrSSTt 
rrSsTt RrSsTt RrSSTt 
rrSsTt RrSsTt RrSSTt 
rrSsTt | rrSsTT | RrSSTt 
RrssTt rrSsTT RrSsTT 
RrssTt mrSSTt RrSsTT 
RrssTt rrSSTt RrSsTT 
RrssTt RRssTt RrSsTT 
RrSstt | RRssTt | RRSsTt 
rrssTt | RrSstt | RrSSt | RRSsTt | RrSSTT 
rrssTt | RrSstt | RrSStt | RRSsTt RrSSTT 
rrSstt RrSstt | RrssTT | RRSsTt | RRSsTT 
rrSstt rrssTT | RrssTT | mSSTT | RRSsTT 
Rrsstt_ | rrSSit | RRSstt | RRssTT | RRSSTt 
rrsstt Rrsstt RRssit | RRSstt | RRSSt | RRSSTt | RRSSTT 
0 1 2 3 4 5 6 
Fic. 63.—-F2 squares of the checkerboard of a cross of red (RRSSTT) X white (rrssil) 
wheat arranged in classes according to the depth of color displayed by the phenotypes. 
z.e., two factors produce twice the depth of red coloration in the grain 
that one produces and all six are necessary for the production of the 
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