54 BREEDING 



The bald statement that he crossed a yellow pea 

 with a green pea leaves one completely in the dark 

 as to the true nature of the character dealt with ; 

 and even the statement that he crossed a yellow- 

 seeded with a green-seeded pea does not make it 

 clear whether by yellow-seeded (for instance) is 

 meant a pea-plant grown from a yellow seed, or a 

 pea-plant which produces yellow seeds. What should 

 be meant by " a yellow pea " or "a yellow-seeded 

 pea " is a pea-plant grown from a yellow seed, because 

 it is the yellow colour of its first two leaves or coty- 

 ledons, seen through the enveloping seed- coat, which 

 is the character with which we are concerned ; and 

 also because, as we shall see later on, a plant grown 

 from a yellow seed does not necessarily produce 

 yellow seeds. 



When a tall is crossed with a dwarf pea the result 

 cannot be seen until the seed resulting from the 

 cross is sown. But the result of crossing a yellow- 

 seeded pea (as defined above) with a green-seeded 

 pea can be seen directly the pod, which has developed 

 from the flower on which the cross was made, is 

 opened. Let me briefly describe here how such a cross 

 is made. A detailed account is given on pp. 146-152. 

 To make a cross between a tall and a dwarf, pollen 

 is taken from a flower of a tall pea and placed upon 

 the pistil in the flower of a dwarf, or vice versa. 

 We will consider the former case. A label is tied 

 round the stalk of the flower of the dwarf plant 

 which has received the pollen from the tall. In due 

 course, the petals wither ; and, if all is well, the pod 



