DISTRIBUTION OF TRIBES. 401 
ing in some places and flourishing and further migrating in others, 
have become gradually differentiated into species which may 
scarcely yet be taken as perfected. 2nd, in the genus Adenostyles, 
which has one Californian and two European species, without any 
known representative in the vast intervening regions of Asia on 
the one side, or of central and eastern North Ameriea on the 
other. "There is no doubt of the generic identity ; the Californian 
species, though quite distinct from either of our European ones, is 
yet more nearly allied to one of them (4. alpina) than the two 
European ones are to each other. Like many others now con- 
fined to America, the genus probably once ranged over a great 
part of the temperate northern hemisphere, and instead of dis- 
appearing from the whole of the Old World, has kept its ground 
in Europe, becoming extinct in Asia. 
It is this same genus Adenostyles which alone supplies some 
sort of link connecting Eupatoriacex with any other tribe ; for in 
habit and involucre it shows some approach to some species of 
Senecio ( Cacalia), although the style and other characters leave no 
doubt as to its being a true Eupatoriacea. 
. Eupatoriacee, within American limits, have formed a number of 
genera, groups of genera, or subgenera, more or less local or 
general, but most of them passing so nearly one into the other as 
to require little notice for the present purpose. The most re- 
markable is perhaps the group or subtribe of Piqueriex, charac- 
terized by the anthers truncate at the top, without that appen- 
dage to the connectivum so universal in the rest of Composite. 
It comprises 7 genera, with about 80 species, chiefly Western, 
ranging from Chili to Mexico, with two or three South-Brazilian 
and three Cuban species; it includes also the above-mentioned 
Adenostemma, to which I shall refer under the head of genera 
with one cosmopolitan species. This remarkable deviation from 
the almost absolute uniformity of Composite is probably, there- 
fore, of West-American origin, and not ancient enough to have 
spread into other continents now severed from America. I have 
not observed it in any other group of Compositie, although the 
appendage may be very much reduced iu a very few tropical 
American Helianthoidez. 
The other deviation I would mention is not so important, nor 
very strictly defined, but purely local. The three genera (or sub- 
genera) Liatris, Trilisa, and Carphephorus form a little North- 
American group, almost limited to the regions east of the Andes or 
2a2 
