6 Weiss, Researches on Heredity in Plants. 



form. Although small, the flowers can be readily cross- 

 pollinated, and the hybrid or cross between these two 

 varieties has scarlet flowers, exactly like those of the 

 scarlet parent. In the second hybrid or filial generation 

 {/ 2), however, 25 % of the plants bear blue flowers, while 

 75 % have scarlet flowers. A bed in which a number of 

 these offspring have been planted out as seedlings offers, 

 when the plants are in flower, a very remarkable and 

 striking illustration of the law of segregation of characters. 



The same result is obtained when plants of the pale 

 salmon or pink varieties are crossed with the blue form. 



Complete dominance of one of the parental characters 

 is, however, not an invariable rule. In some cases the 

 first filial generation shows approximately an intermediate 

 condition of the parental features. Thus Correns has 

 shown that crossing a white and red form of Mirabilis 

 results in a plant with pink flowers. If this plant, how- 

 ever, is self-fertilised, the resulting plants produce white, 

 pink, and red flowers in the proportion of i : 2 : i. In 

 this case the heterozygous pink form can always be 

 clearly distinguished from the homozygous red, though 

 they must both be regarded as dominants. 



Considerable interest attaches to the curious results 

 obtained by Bateson in crossing two white sweet peas 

 belonging to the variety Emily Henderson. The resultant 

 cross, instead of bearing white flowers, as might have been 

 expected, produced parti-coloured flowers (red and purple), 

 very like the form known as Purple Invincible. The 

 explanation of this curious phenomenon lies in the fact, 

 now definitely established, that the production of colour 

 in these flowers depends on two factors, which must 

 both occur in one plant before the flowers can become 

 coloured. In the two white forms these factors were 

 segregated, hence the absence of colour in the two parents. 



