470 MR. G. BENTHAM ON COMPOSITA. 
Islands; and one species carried out with man to extratropical $. 
America, has there found circumstances so congenial to its consti- 
tution that, as a successful eolonist, it has overpowered the native 
vegetation over vast tracts of country. None are truly Àmerican 
or high-northern. 
Cousinia is another genus of true Thistles, differing from Carduus 
and Cnicus in the slender, fragile, usually small and exceedingly 
caducous setze of the pappus, and remarkable for the large number 
of species confined to a small area. Above 100 well-marked species 
have been described ; and many more exist in our herbaria, although 
the whole genus is limited to Western and Central Asia, the chief 
centre of its range being in Persia; and at its western extremity 
it barely reaches the Mediterranean. 
Arctium is a small European and temperate Asiatic genus, of 
which the number of species, whether two or seven or eight, is a 
matter of contention, and which, though not prickly, is but a slight 
divergence from Carduus, with a pappus nearly that of Cousinia. 
The Carlina group includes three closely allied genera which 
might be treated as one—Carlina itself, fourteen species, Atrac- 
tylis, about the same number, and Thevenotia, two species. They 
connect the Carduus and Cnicus group with the Xeranthema. 
With the prickly thistle-like aspect of the former, they have the 
densely villous achenes and simple series of more or less paleaceous 
pappi of the latter. Geographically they are widely spread, 
although they do not reach America. Their chief seat is the 
Mediterranean region; and one or two species extend over the 
greater portion of Europe and extratropical Asia. They have 
also, always within their general Old-World range, established 
some local forms distinct enough to have been often considered 
genera. These are Carlowitzia (belonging to Carlina), two species 
in the Canary Islands, Thevenotia, two species in Persia, and 
Atractylodes (now reduced to Afractylis), two species in Japan 
and China. Atractylis Preauaii is another Canary-Island form, 
which might almost be regarded as sui generis. The corollas of 
the sterile florets at the circumference of the capitula in Atrac- 
tylis assume the palmate or 5-merous ligulate form which, as in 
Stokesia, indicates an approach to the Cichoraceous corollas, not to 
those of the rays of ordinary radiate capitula. 
Xeranthemum, four or five species, and the closely allied mono- 
typic Chardinia and Siebera form a small very distinct group of 
Cynaroidez, limited to their great centre the Mediterranean 
