440 Thiselton-Dyer. — Morphological Notes. 
with hybrid plants raised from species which have not been 
cultivated, while with those which have been long cultivated 
they are of frequent occurrence. . . . Max Wichura, who 
worked exclusively on willows, which had not been subjected 
to culture, never saw an instance of reversion 5 (Darwin, loc. 
cit., 50). I have already quoted Darwin’s dictum that : ‘ As 
a general rule, crossed offspring in the first generation are 
nearly intermediate between their parents, but,’ he adds, ‘ the 
grandchildren and succeeding generations continually revert, 
in a greater or less degree, to one or both of their progenitors.’ 
It is to this fact, I suppose, that an attempt is made to give 
expression in what is called Mendel’s law. It would have 
been very interesting to have seen what would have happened 
to K . kewensis in succeeding generations. Unfortunately, so 
far every attempt to raise seedlings from it has failed. The 
capsules form with every promise of fertility, but only contain 
shrivelled rudiments of seeds. But had this been otherwise, 
it by no means follows that its characters would have shown 
any dissociation. Wichura ‘ found in opposition to Naudin 
that the progeny of hybrid willows retains its hybrid character’ 
(Romanes, loc. cit., 426). 
While writing these lines the important paper by De Vries 
(Comptes rendus, 2 Fevr., 1903, pp. 321-3) comes into my 
hands. It confirms the suspicion which I have long enter- 
tained that Mendel’s law is not of universal application. 
DeVries lays it down that : ‘La loi de Mendel s’applique aux 
caracteres dits de variete, tandis que les caracteres specifiques 
vrais donnent dans leurs croisements des caracteres d’hybrides 
constants.’ Such characters ‘ne se disjoignent pas ; ils restent 
les memes dans les generations successives. J’ai verifie ce fait 
par quatre generations d’un hybride entre les CEnothera 
muricata , L., et CE. biennis , L., et j’ai etudie a ce point de 
vue diffdrents autres hybrides, notamment dans le meme 
genre.’ 
The explanation depends probably on the principle of 
specific stability, on the importance of which I have else- 
where insisted. From this point of view a hybrid may carry 
