244 Particoloured Peas [ch. xiii 



for seeds of yellow varieties turn yellow before they harden, 

 while the particoloured sorts bleach after they have become 

 ripe. 



In some yellow varieties greenish seeds occur. This 

 phenomenon, the converse of the last, occurs in wet 

 years with many kinds, some of course being specially 

 liable. 



The fact that such differences are fiuctuational and not 

 genetic appears at once when breeding is begun ; for if in 

 a green which bleaches {e.g American Wonder) the yel- 

 lowest and the greenest are taken from the same plant and 

 sown, there will be no corresponding difference between 

 their respective produce. By selecting the greenest and 

 yellowest from a large mass of commercial seeds of a variety, 

 not harvested plant by plant, some correspondence may be 

 obtained occasionally \e.g. Telephone) — but the occurrence 

 merely means that the mass, though called one variety, had 

 not really been selected down to a ''pure line," but was in 

 fact a mixture of sorts. In such a type as "Nonpareil," for 

 instance, where the difference between yellows and greens 

 is actually genetic, the yellows and the greens will give dis- 

 tinct results. "Nonpareil," in fact, is a form which consists 

 of true yellows and true greens in about equal numbers, and 

 it is simply a mixture of two varieties not sensibly different 

 except in seed-colour. No doubt it arose from a plant 

 saved in one of the later generations derived from a cross, 

 which plant was homozygous in other respects but hetero- 

 zygous in seed-colour. 



