MENDELISM 



133 



inbreeding, four different types of coloured flowers in the 

 offspring : the dominant red type, the recessive cream 

 type, and two new types — one having a red-cream, the 

 other a white colour of the flower. 



The explanation is as follows : The red colour of the 

 flower is due to red sap, which is dominant to colourless 

 sap. The cream colour, on the other hand, is due to yellow 

 corpuscles, and is recessive to colourless corpuscles. We 

 get, accordingly, after W. Bateson, the following scheme, 

 which explains itself : 



Red Variety x Crearn Variety. 

 Two allelomorphic pairs : 

 I, Red Sap— D 



Colourless Sap— R 



2. Colourless Corpuscles — D 

 Yellow Corpuscles — R 



Red Sap ] 



+ V=Red 



Colourless CorpusclesJ 



Red Sap : Red Sap : Colourless Sap : Colourless Sap : 



Colourless Yellow Colourless Yellow 



Corpuscles Corpuscles Corpuscles Corpuscles 



Appearance : 



9 Red 3 Red-Cream 3 White 1 Cream F2 



Fig. 55. — Coloured Flowers. (After Bateson.) 



A similar case is presented by the combs of fowls. We 

 can distinguish four kinds of combs : (i) A large serrated 

 single comb, as in the Leghorn and Andalusian breed ; 

 (2) a flattened papillated " rose " comb, as in the Wyan- 

 dottes and White Dorking ; (3) a threefold-ridged comb, 

 the " pea " comb, in the Indian game fowl ; and, lastly 

 (4) the corrugated " walnut " comb of the Malay fowl. 



Both rose and pea comb are dominant to the single 

 comb ; while the cross between the rose and pea comb 

 gives a walnut comb, which on further inbreeding produces 

 the usual four Mendelian types, in the proportion of nine 

 walnut, three rose, three pea, and one single. 



The explanation is similar to that given in the previous 



