iii VARIABILITY OF SPECIES IN A STATE OF NATURE 77 
many large genera. As examples we may take the roses, the 
brambles, and the willows as well illustrating this fact. In Mr. 
Baker’s Revision of the British Boses (published by the Linnean 
Society in 1863), he includes under the single species, Kosa 
canina — the common dog-rose—no less than twenty-eight 
named varieties distinguished by more or less constant characters 
and often confined to special localities, and to these are 
referred about seventy of the species of British and continental 
botanists. Of the genus Rubus or bramble, Jive British species 
are given in Bentham’s Handbook of the British Flora , while 
in the fifth edition of Babington’s Manual of British Botany, 
published about the same time, no less than forty-five species 
are described. Of willows (Salix) the same two works 
enumerate fifteen and thirty-one species respectively. The 
hawkweeds (Hieracium) are equally puzzling, for while Mr. 
Bentham admits oidy seven British species, Professor Babing- 
ton describes no less than thirty-two, besides several named 
varieties. 
A French botanist, Mons. A. Jordan, has collected numerous 
forms of a common little plant, the spring whitlow-grass 
(Draba verna); he has cultivated these for several successive 
years, and declares that they preserve their peculiarities un¬ 
changed ; he also says that they each come true from seed, 
and thus possess all the characteristics of true species. He 
has described no less than fifty-two such species or permanent 
varieties, all found in the south of France ; and he urges 
botanists to follow his example in collecting, describing, and 
cultivating all such varieties as may occur in their respective 
districts. Now, as the plant is very common almost all over 
Europe and ranges from North America to the Himalayas, 
the number of similar forms over this wide area would prob¬ 
ably have to be reckoned by hundreds if not by thousands. 
The class of facts now adduced must certainly be held 
to prove that in many large genera and in some single species 
there is a very large amount of variation, which renders it 
quite impossible for experts to agree upon the limits of species. 
We will now adduce a few striking cases of individual 
variation. 
The distinguished botanist, Alp. de Candolle, made a special 
study of the oaks of the whole world, and has stated some 
