310 LOCK : STUDIES IN PLANT BREEDING 
(cotyledons) was less developed and at first may easily be 
overlooked.” The cause of the partial disappearance of the 
green coloration, as Mendel states, has no connection with 
the hybrid character of the plants, as it likewise occurs in 
the parental variety. These observations are fully borne 
out by the case of the pea Telegraph. They apply in an even 
more marked degree to the variety Telephone (Sutton’s). The 
point is worth notice on account of Weldon’s criticism (76) 
of Mendel’s work, in which stress is laid upon the excep¬ 
tional behaviour of Telephone. 
Example //.-—Larger figures were obtained in the case of 
a cross between two races of Indian corn (Zea Mais), u Black 
Mexican ” and “ Boone County White.” The former is 
characterized by a sugar endosperm and wrinkled grain, and 
the latter by a starchy endosperm and indented grain. The 
sugar corn was used as the pollen parent, and the form of 
the grains (F x ) on the indent parent was unchanged, the sugar 
character being completely recessive as xenia. From these 
grains plants were grown, which were allowed to mutually 
pollinate one another. There resulted—upon 18 cobs taken 
each from a separate plant—7,075 grains (F 2 ), of which 5,310 
showed the starch character and 1,765 the sugar character: 
the proportion being therefore 75*06 per cent, of starchy 
grains to 24*94 per cent, of sugar grains, or 3 : 1. 
(2) Mendelian Dihybrids. 
Heterozygotes from parents which differ in two pairs 
of allelomorphs, one member of each pair being dominant. 
For the sake of clearness we may write A and a for the 
allelomorphs of one pair, B and b for those of the other. 
(The parents show, e.g ,, AB and ab respectively.) A and B 
are dominant, a and b recessive; F 1 the cross-bred generation 
exhibits AB to the exclusion of ab, but in reality includes 
AaBb. 
In F 3 the visible combinations AB, Ab, aB, ab, appear in 
the proportion ;—9 : 3 : 3 ; 1. 
