158 ARTIFICIAL FERTILISATION 



caucasicum by R. cinnamomeum, and the hybrid from this 

 latter cross crossed again with R. Edgeworthii, and especially 

 the Sikkim species R. virgatum crossed with another of my 

 hybrids, R. ciliatum by R. Edgeworthii all having more the 

 foliage and the aspect of the mother than the father. 



I have another hybrid of the same R. virgatum, the female 

 parent crossed, I believe, by Rhodothamnus chamacistus, a tiny 

 procumbent plant of three inches, but all set with flower-buds 

 not, as in the male parent, at the tips of the shoots, but, as 

 in the female, at the axils of the leaves. I have stated my 

 belief that the Rhodothamnus is the male parent, but I cannot 

 do so confidently, from the tallies having got into confusion 

 the specimens being planted out. But as some plants were 

 obtained from that cross, and as this is the smallest, I regard 

 it as likeliest to be the true progeny ; and the cross being an 

 extreme one a mule, in fact it is open to question. But as 

 I have this season effected still more extreme certainly more 

 unlikely crosses in that family, where there could be no mis- 

 carriage, you may, I think, take it as true in the meantime. I 

 could overwhelm you with proof. Darwin, at page 333 of the 

 last edition of his ' Origin of Species,' has observed the above 

 tendency. "When two species," he says, "are crossed, one 

 has sometimes a prepotent power of impressing its likeness on 

 the hybrid; and so I believe it to be with varieties of plants." 



Naturalists of the highest note Gaertner, Kolreuter, Naudin, 

 and Wichura are far from being at one on the subject of varia- 

 bility, as Darwin has shown, especially as relates to crosses, 

 ist, between species and species; 2d, between species and 

 varieties ; 3d, between mongrel offspring. But this is a com- 

 plex subject ; and when such high authorities are not at one, 

 and Darwin admits that he cannot reconcile them, it is manifest 

 that the case is still open to further probation. In dealing 

 with the views of Gaertner, to whose testimony he deservedly 

 accords great value (page 331), Darwin says that Gaertner, 

 whose strong wish "it was to draw a distinct line between 

 species and varieties, could find very few, and, as it seems to 

 me, quite unimportant, differences between the so-called hybrid 

 offspring of species and the so-called mongrel offspring of 

 varieties. And, on the other hand, they agree most closely in 

 many important respects. The most important distinction is, 

 that in the first generation mongrels are more variable than 

 hybrids ; but Gaertner admits that hybrids from species which 

 have long been cultivated are often variable in the first genera- 

 tion ; and I have myself seen striking instances of this fact. 

 Gaertner further admits that hybrids between very closely allied 



