LATENT CHARACTERS 197 



florists as Purple Invincible, which is characterized by 

 a purple standard and blue wings. The pollen pro- 

 duced by these plants was of the long type. Thus as 

 regards the shape of the pollen grains there was simple 

 dominance. But the union of two white-flowered 

 types has given rise to a series of plants all possessing 

 a definite colour character purple with blue wings. 

 This character is very probably the same as that 

 exhibited by the common ancestor of all our cultivated 

 sweet-peas. Here, then, we seem to have a clear case 

 of reversion to the ancestral type on crossing. We 

 shall find that the Mendelian principles will enable us 

 to arrive at a clear conception of the mechanism of 

 this process. 



The cross-bred plants were self-pollinated, and in F 2 

 the following types made their appearance in approxi- 

 mately the proportions given : 



J 



Painted Lady is a well-known colour type which is 

 characterized by the presence of a red standard and 

 white wings. Picotee and tinged white are also forms 

 well known to the sweet -pea fancy. They appear to 

 be diluted forms of the purple and Painted Lady types 

 respectively, their appearance depending upon the 

 presence of a definite diluting factor in addition to the 



