PLANT BREEDING 349 
tions by use of the Mendelian theory. For example, two or more 
hereditary factors may be necessary for the production of an actual 
tangible character. If factors A and B must be present for its pro- 
duction, then a plant carrying only factor A and another carrying only 
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Fic. 6. MBNDELIAN SEGREGATION IN MAIzn, a and b, the two parents, starchy 
and sweet maize; c, the first hybrid generation showing dominance of starchiness ; 
d, the second hybrid generation showing segregation with the ratio of three starchy 
to one wrinkled seed. Lower row daughters of d. e, f and g, results of planting 
starchy seeds. One ear out of three is pure starchy. h, result of planting sweet 
seeds. Har is pure sweet. 
factor B do not possess the character. But let the two plants be crossed 
and the character appears. There are two white varieties of sweet peas ; 
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each, however, contains one of the two factors necessary for the pro- 
