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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 



Fig. 6. Mendelian Segregation in Maize, 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. Ear 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 ; 

 each, however, contains one of the two factors necessary for the pro- 



