314 Varieqathn In Primula sinensis 



usual way. When the cidorina $ is crossed with albumuculata ^^ , the 

 hybrids so formed are indistinguishable from hybrids between the 

 chlorina and the normal green races, both in appearance and in the 

 progeny to which they give rise. That is to say, the pollen grains of 

 the albomaculata race, even when they are produced by flowers borne 

 on the white branches, nevertheless caiTy the fiictor for normal 

 green, as distinguished from the pale green of the chlorina. In these 

 races there are, therefore, two distinct characters of the chloroplasts, 

 one of which is inherited through the mother only, while the other is 

 inherited in the usual maimer. Correns suggests' that these facts may 

 be explained by means of an hypothesis based on the assumption, which 

 has received some degree of support from cytological observations, that 

 in the process of fertilization in the higher plants the nucleus of the 

 male gamete passes over to the egg-cell alone and unaccompanied by 

 any cytoplasm, so that the cytoplasm of the zygote is entirely of 

 maternal origin. The germ-cells of the albomaculata race are regarded 

 as possessing nuclei which are perfectly normal and carry the factor for 

 the typical green leaf-colour ; the cytoplasm of the germ-cells, however, 

 in correspondence with the mosaic of which the plant consists, is either 

 normal or chlorotic ("gesund oder chlorotischkrank ") and, accordingly, 

 either permits or prevents the development of normal gi-een chloro- 

 plasts. Assuming the cytoplasm of the zygote to be entirely of maternal 

 origin, the offspring of a variegated albomaculata plant are, therefore, 

 green, variegated or yellow, according as the cytoplasm of the egg-cells 

 is entirely normal, a mosaic of normal and chlorotic components, or 

 entirely chlorotic. 



In formulating this hypothesis, Correns'' leaves it an open question 

 whether the seat of the abnormality in the chlorotic plastids is to be 

 looked for in the plastids themselves, or in the cytoplasm which surrounds 

 them. Baur, in discussing his experiments on Pelargonium", inclines to 

 the former alternative ; Correns regards the latter as at least equally 

 possible in Mirabilis. 



In Primula no form is yet kno^vn corresponding with the chlorina 

 races of Mirabilis, but the maternal inheritance of the variegated and 

 yellow-leaved characters in Primula corresponds exactly with that of 

 the albomaculata character in Mirabilis and is, I think, to be explained 

 on lines similar to those put forward by Correns. But the evidence 



' Zeitschr. f. Ind. Abst.- u. Vererbunr/slehre, ii. p. 331, 1909. 



= L.C. p. 332, footnote (2). 



' Zeitschr. f. Ind. Abst.- ii. Vererbvngslfhi;; i. pp. 348 ff., 1909. 



