INHERITED SEED-CHARACTERS 6^ 



recessive). The inheritance of these characters is 

 precisely analogous to that of the colour of the 

 cotyledons ; and a diagrammatic representation of it 

 may be made by substituting round for tall and 

 wrinkled for dwarf in the Frontispiece. 



The shape of the seed (whether round or wrinkled) 

 is determined by the cotyledons, and not by the 

 seed-coats ; we may therefore say that the pair 

 of characters is roundness of the first two leaves of 

 the plants and wrinkledness of these structures. 

 The shape of the cotyledons, therefore, is just as 

 valuable a character, for the reasons stated above, 

 as their colour, to experiment with for the purpose of 

 testing general statements with regard to the Men- 

 delian phenomenon. But over and above this it 

 possesses an interest which the colour of the cotyledons 

 does not. In the first place, the distinction between 

 round and wrinkled peas is one of great economic 

 importance, the nature of which will be fully discussed 

 later ; and in the second place, it is possible in the 

 case of this character to see below the surface, as it 

 were, of the Mendelian phenomenon, and thus to 

 obtain a truer view of the essential nature of this 

 process. But at present we are concerned with the 

 phenomena as they present themselves to the senses 

 unaided by the microscope and the scales. Fig. 21 

 represents the result of crossing of round-seeded with 

 wrinkled-seeded pea. The round cotyledons of the 

 first hybrid generation do not differ, so far as the 

 unaided eye can see, from those of the round 

 parent. 



