3 1 2 Appendixes 



Appendix to Chapter VI 11. 



In this chapter an attempt Is made to discuss the 

 relation of self-coloured to pled types In the simplest 

 possible cases, such as that of the self-coloured and pled 

 rabbits. All further researches on this subject tend to 

 show that it Is one of great complexity. Even in animals 

 the Interrelations of the various degrees of pledness are not 

 established satisfactorily for any one example, and In plants 

 there are evidently phenomena to be explored which as yet 

 evade our analysis. In the case of the flaked flowers of 

 Mirabilis for example the experiments of Miss Marryat 

 showed that though the numbers suggest orderly behaviour, 

 it was not possible yet to express them in factorial terms, 

 and the same Is true for PiHrnula Sinensis. In resfard to 

 variegation of the leaves of Mii^abilis Correns has published 

 some very remarkable evidence. In an earlier paper, Zts.f. 

 indiikt. Abstam., 1909, i. p. 291^, he showed that a peculiar 

 variegated type which he called variegata usually behaved 

 as a recessive to the normal green. Sometimes however 

 this variegated form bears a branch entirely green. The 

 self-fertilised offspring of the variegated and of the green 

 branches were separately studied ; and it w^as found that 

 the variegated branches gave families consisting almost 

 entirely of variegated -f a small and irregular percentage 

 of greens; but the green branches gave normal Mendelian 

 families, of 3 greens : i variegated, 25 per cent, of the 

 greens being pure greens, the rest heterozygous. The 

 variegateds and the greens, of whatever origin, behaved in 

 the same way. 



As regards the striping of the flowers in Mirabilis 

 Correns has also provided some new evidence. When 

 a plant bears both striped branches and unstrlped branches, 

 each type produces offspring which in the great majority 

 resemble Itself. The striped offspring then throw a small 

 and irregular proportion of self-coloured, but the self-coloured 

 consist of heterozygotes and homozygotes approximately In 

 the ratio 2:1. The facts in Correns's opinion indicate that 

 a homozygous branch can by some change pass Into a 



*' For further discussion of cognate phenomena see Correns, ibid. 11. 



1909. p. ZZ-^' 



