182 ORIGIN OF NON-SEXUAL CHARACTERS 



the pollen is almost entirely sterile. It has therefore 

 been propagated by crossing with Lamarchiana 

 pollen, with the result that both forms are obtained 

 with lata varying in proportion from 4 per cent, to 

 45 per cent. 



Rubrinervis is a mutation from Lamarchiana, 

 chiefly distinguished by red midribs in the leaves 

 and red stripes on the sepals. When propagated 

 from self-fertilised seed it produced about 95 per 

 cent, of offspring with the same characters, and the 

 remaining 5 per cent, mutants, one of which was 

 laevifolia which had been found by De Vries among 

 plants growing wild at Hilversum. Gates obtained 

 a single plant among offspring of rubrinervis in which 

 the sepals were red throughout, and to this he gave 

 the name rubricalyx. When selfed this plant gave 

 rise to both rubricalyx and rubrinervis, and in the 

 second generation when the rubricalyx was selfed 

 again the numbers of the two were approximately 

 3 to 1. Rubricalyx is therefore a dominant hetero- 

 zygote, and this fact was further confirmed in the 

 third generation when a selfed plant gave 200 

 offspring aU rubricalyx, the mother plant having 

 evidently been homozygous for the red character. 

 In this case, therefore, we have what Bateson was 

 seeking, the origin of a new dominant character 

 under observation, the original mutation having 

 arisen in a single gamete of the zygote which gave rise 

 to the plant. It is claimed by mutationists that 

 mutations are not new combinations or separations 

 of Mendelian unit characters already present, but 

 are themselves new characters, though not always 

 necessarily, as in the case of rubricalyx, new unit 

 characters in the Mendelian sense. 



