IN THE TROPICS: III. 131 



F1. 



Expt. 54. — Yellow dent x Black Mexican sugar corn. 



On a plant of Riley's Favourite growing close to plants of 

 Black Mexican there were found 5 grains of a bri ghtly mottled 

 black and yellow colour amongst the normal yellow grains. 

 These grains were clearly of the above parentage. It may be 

 noted at once that in later generations none of the grains showed 

 this mottled character, though the black pigment was of course 

 present in many of them. This fact may be compared with 

 the abundance of speckled grains in F't and F 2 from the cross 

 White dent x Black sugar, and their absence from later genera- 

 tions of the same, as well as from all the individuals of the 

 mongrel strain described later on, the latter being doubtless 

 still further removed from the original cross from which 

 we must suppose them to be descended. 



The shape of these 5 grains was exactly like that of the 

 surrounding grains of the same cob. 



F2. 



3 plants arose from the above grains and their Mowers 

 received pollen from flowers of white dent , with the following 

 result :- 



All the grains were of a semi-dent form and showed no trace 

 of the sugary character. The black grains were all of a deep 

 and uniform colour. We must suppose that there was defective 

 dominance of black in the case of No. 1, whilst there was full 

 dominance of black in Nos. 2 and 3, in which case the expected 

 number of grains would be 50 per cent. 



