272 Noji-Isolable Races. 



qiiadn" 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 wdiite- or yellow- 

 edged leaves occur only rarely. I observed an instance 

 of the latter in a wnld specimen of Oenothera Lainarck- 

 iana (1887, see. Vol. I, p. 480) and of the former I 

 found specimens in Spiraea Ulmaria, Calluna vulgaris, 

 TrifoJium pratcnse, Lychnis diurna in 1886 and 1887 in 

 the neighborhood of Hilversum. In the above mentioned 

 years I found 3^ellow variegated plants of Planfac/o major, 

 Phalaris arnndinacea, Rhinanfhns major, Erica Tetralix, 

 Urtica nrens, Hypericum perforahini, Trifoliitni pra- 

 tcnse, Hieracitini Pilosella, Rubiis frnticosns. Polygonum 

 Convolvulus and Genm nrhanum. 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 Thymus 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 ])ut 

 that they have been preceded by many generations of 

 purelv green ancestors; so for instance in Chrysanthe- 



