274 Non-Isolablc Races. 
reversion to the parental form. It is especially common 
on woody species and in shrubs. Evonymus japonica, 
Quercus pedunculate,, Weigelia amabilis, Cornus san- 
g nine a and many others afford well-known examples. 
Others are found amongst perennials and perhaps best 
of all in Arabis alpina. I may cite as further instances 
partly from the literature on the subject and partly from 
my own observations : Castanea vcsca, Kcrria japonica, 
Aesculus Hippocastanum, Yucca pcndula aiirca, Ulinns 
campestris, Zea Mays, Rub us fruticosus and so on. 
The 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 
o 
it is easy to separate these and cultivate them further. 
Analogous cases of this double reversion, as it may be 
called, were observed by me in 1893 in Castanea vcsca 
variegata and Kcrria japonica variegata 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 
