274 Non-Isolahlc Races. 



reversion to the parental form. It is especially common 

 on woody species and in shrubs. Ei'onymus japonica, 

 Oucrciis pcdiinctilata, Weigelia amahilis, Corniis sail- 

 guinea and many others afford well-known examples. 

 Others are found amongst perennials and perhaps best 

 of all in Arabis alpiua. I may cite as further instances 

 partly from the literature on the subject and partly from 

 my own observations: Castanca vesca, Kevria japonica, 

 Acsculns Hippocastanmn, Yucca pendida aiirea, Ulnnts 

 cainpestris, Zca Mays, Rubus fruticosus and so on. 



Tlie green branches can obtain nutrition better than 

 the variegated ones. Therefore they grow^ more vig- 

 orously and become stronger during the course of 

 years, and very often overgrow the others. As a rule 

 all their leaves and branches are pure green, and they 

 look as if they had entirely lost the capacity for varie- 

 gation. But this is not the case, for sometimes we see 

 single variegated twigs on these green branches. Arabis 

 alpina is especially instructive in this connection, for it 

 often gives rise to variations from its buds, and since 

 it is easy to separate these and cultivate them further. 

 Analogous cases of this double reversion, as it may be 

 called, were observed bv me in 1893 in Castanca vcsca 

 varlcgata and Kcrria japonica varicgata which bore a 

 little variegated twig on a green branch; and the same 

 has been observed in other cases. 



The deficient nutrition frequently makes the varie- 

 gated leaves smaller than the green ones. If the pigment 

 IS mainly absent in the margin of the leaves this becomes 

 too small for the middle area and the whole leaf becomes 

 crumpled. A unilateral checking of the growth leads 

 to a corresponding bending. It is due to these circum- 

 stances that the habitus of variegated plants is often so 



