= male gametes 



= 9 dark brown, 

 6 light brown 

 and 1 white. 



i.e. — The presence of both factors A and B in the same plant has a 

 cumulative effect with regard to intensity of color. 



(b) When a certain brown-chaffed wheat was crossed 

 with a white-chaffed strain Fi gave brown-chaffed, but 



Fo gave 15 brown-chaffed and 1 white-chaffed. Here 

 again there are two dominant factors for brown and 

 two recessive factors for white. Make out a diagram 

 after the manner in (a). i 



(c) When a certain red-seeded wheat was crossed with a 

 white-seeded strain F] were red, but F2 gave 63 red 

 and 1 white. In this case there are three dominant 

 factors for the red and three recessive allelomorphic 

 factors for white. Make out a diagram. 



ShuU furnishes an interesting case where a triangular - 

 capsuled Shepherd's Purse was crossed with a round-cap- 

 suled form. Fi gave all triangular capsules, but F2 gave 15 

 triangular and 1 round. Make out a diagram on the sup- 

 position that the plants with the top-shaped capsules have 

 two recessive factors and have the genetic constitution 

 ccdd and the pure plants with triangular-shaped capsules 

 the genetic constitution CCDD. 



Problem. — Analyse the following results: the Fo ratio 

 when certain black beans are, crossed with certain white 

 beans is 12 black : 3 yellow : 1 white. 



Castle's experiments with crosses of lop-eared and short- 

 eared rabbits show that probably four or more factors for 

 ear-length occur hence grand-parental recessive types are 

 not likely to appear in breeding, and that all gradations 

 of ear-length would occur. 



East's experiments with corn show that length of ear, 

 height oj plant and productivity depend on multiple factors. 



Mendelists are inclined to believe that skin color as a 

 result of crosses between negroes and whites is not a case of 

 Blended inheritance but of Mendelian segregation where 

 several multiple factors for color are concerned. (C. B. 

 Davenport, Heredity of Skin Color in Negro- White Crosses, 

 No. 188 Carnegie Inst. Wash.) 



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