272 Non-Isolable Races. 
quaclri foliate leaves, etc.) only in isolated organs and 
parts of organs. Some sorts I regard as analogous to the 
double varieties, whilst the aurca varieties are probably 
just as constant as the Varietatcs discoidcac and as the 
best elementary species. 
The very general occurrence of variegated plants 
points to the conclusion that the latent capacity for varie- 
gation is widely distributed throughout the vegetable 
kingdom. Moreover the fact that branches and whole 
plants with this character are met with every year in 
new species both in the garden and the field points in the 
same direction. In this connection I may mention the 
fact that forms with white variegated or white- or yellow- 
edged leaves occur only rarely. I observed an instance 
of the latter in a wild specimen of Oenothera Lamarck- 
iana (1887, see. Vol. I, p. 480) and of the former I 
found specimens in Spiraea Uhnaria, Callnna I'ulgaris, 
Tri folium pra tense, Lye Jin is dinrna in 1886 and 1887 in 
the neighborhood of Hilversum. In the above mentioned 
years I found yellow variegated plants of Plantago major, 
Phalaris arundinacea, Rhinanthus major, Erica TetralLv, 
Urtica nrens, Hypericum perforatum, Tri folium pra- 
tcnse, Hleraciuni Pilosella, Rnbns fmticosus, Polygomun 
Convolvulus and Genm nrbanum. In 1869 I found a 
beautiful variegated specimen of Arnica montana in the 
Thuringian Forest and later one of Plantago lanceolata 
in Saxon Switzerland, and one of Thyinus Serpyllum 
near Wyk aan Zee in Holland (Fig. 54), and I have 
since frequently found occasional variegated specimens 
of other wild species. In the same way they appeared 
in my own cultures where there can be no question but 
that they have been preceded by many generations of 
purely green ancestors; so for instance in Chrysanthe- 
