392 READINGS IN EVOLUTION, GENETICS, AND EUGENICS 
hybrid progeny would all be tall, smooth, yellow, since these three 
characters are dominant. Inbreeding the hybrids gives the following 
result in the F, generation: 27 tall smooth yellow, g tall smooth green, 
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Fic: 69.—Diagram illustrating dihybrid ratio. Upper part shows how original 
parents were crossed to give F,; hybrid; lower part shows F, hybrid producing 
four kinds of gametes; chance matings among these gametes, when F; is inbred, 
result as indicated in the large set of squares and explains the 9:3:3:1 ratio in 
the F, generation. (From Coulter and Coulter.) 
g tall wrinkled yellow, 9 dwarf smooth yellow, 3 tall wrinkled green, 
3 dwarf smooth green, 3 dwarf wrinkled yellow, 1 dwarf wrinkled 
green. The trihybrid ratio therefore is 27:9:9:9:3:373:1. This 
involves 64 individuals and 8 phenotypes, 
