306 Varicf/atioii in Primula sinensis 



Antirrhinum the yellowish-white plants, which are entirely devoid of 

 normal chloroplasts, do not survive beyond the seedling stage, in 

 Primula it has been found possible to raise a few examples of the 

 corresponding ])ale-coloured typo to maturity and to use them both as 

 the female and as the male parents in crosses. 



The pale yellow or yellowish-green plants oi Primula differ from the 

 normal green type in having smaller chloroplasts, which are of a pale 

 yellowish-gi'een colour, instead of being bright green. There is some 

 variation among the yellow-leaved plants as regards the degree of 

 chlorosis'; some are very pale, others are a greenish -yellow, the 

 differences in appearance being due to difference in the size and pig- 

 mentation of the chloroplasts. The variegated plants consist of a 

 patchwork of cells of two kinds, containing respectively bright green 

 and pale-c(jlour(xl chloroplasts. In the mature organs of the variegated 

 plants, the individual cells, at any rate in the great majority of cases, 

 contain chloroplasts of one kind only, but evidence has been obtained 

 that in the very young leaves two kinds of chloroplast may be present 

 together in the same cell. The bearing of this observation on the 

 genetic problem of the maternal transmission of variegation is dis- 

 cussed on pp. 314-317. 



As in Mirabilis and Antirrhinuni, the \ariegated plants oi Primula, 

 when self-fertilized, give three kinds of offspring, namely, self-coloured 

 green, variegated and self-coloured yellow, in irregular proportions. 

 The green offspring of a variegated plant give only green progeny in 

 succeeding generations, the variegated continue to give all three types. 

 Most of the yellow-leaved plants die at an early stage, but a few indi- 

 vidtials have been brought to flower; I have not succeeded in obtaining 

 seeds from the self-fertilization of these plants, but they have been 

 crossed with normal green plants. The result of these experiments is 

 to shew that, apart from any question of variegation, the character of 

 the chloroplast is transmitted through the egg-cell only ; when the 

 yellow plant is used as the female parent all the offspring are yellow ; 

 when it is used as the male parent, in a cross with a green plant, both 

 the Fi and the succeeding generations consist entirely of self-coloured 

 green plants, the yellow character not having been transmitted to the 



' As the term "chlorosis " in some sense connotes disease, it should be said that the 

 term is used in this paper in a purely descriptive sense, applied to a condition of the 

 plants. The chlorosis in Primula is inherent in the plant and is not due to methods 

 of culture. Nor has it anything to do with the "infectious chlorosis" of some plants (see 

 Baur, loc. rit.). 



