266 Non-Isolable Races. 
vegetable kingdom and occurs in all the larger groups 
and especially in most families of flowering plants. 1 
At that time some of the most widely cultivated forms 
were the ribbon grass, Phraguiitcs arundinacca I'aricgata, 
and the variegated holly, Ilex Aquifoliiiin. Both are 
still much grown in gardens, the ribbon grass being rela- 
tively uniform, the holly highly variable. Of the latter 
there is a variety with white-edged leaves, besides the 
ordinary one with flecked leaves. Phragmites is differ- 
ent in many respects from genuine variegated plants and 
is much less variable in its character. The Ilc.r, however, 
is highly variable and often bears green shoots which 
may soon supersede the others on account of the greater 
facility with which they can obtain nourishment. A fine 
variegated bush of this species, or of any other, may be- 
come entirely green, whenever the green branches are 
not cut away every year. Thus it is probable that many 
specimens of the holly, which are now quite green, were 
originally variegated and were bought and planted as 
such. On closer examination we often find on them an 
occasional variegated twig which proves the correctness 
of this supposition. This is also the case with the horse 
chestnut, of which many older trees still living were 
planted at a time when the variegated variety was in 
special favor. Since then their foliage has become green 
and their original character is no longer seen. But an 
occasional checkered branch, or even the numerous small 
twigs with white leaves along the main stem, betrays the 
original variegated condition of the specimen. In the 
same way many cases of single variegated twigs on 
green bushes and trees are not to be regarded as the indi- 
1 SCHLECHTENDAHL, Liiuiaea, 1830, V, p. 494. Very little seems to 
be known about variegated mosses and thallophytes. 
