REGIONS AND AREAS OF DISTRIBUTION. 519 
The characteristic tribes of the Mexican region are, in the first 
place, the Helianthoidez, Helenioides, and homochromous Aste- 
roidex ; and, secondly, the Eupatoriaces, the former including 
most ofthe small endemic genera which mark the region as a 
great centre of preservation of ancient forms, the latter exhibiting 
the genera which appear to be now in the greatest degree of pros- 
perity. In the remaining Asteroides, Vernoniaces, Gnaphalioid 
Inuloidez, and even Senecionides the endemic genera are few, 
and those which have numerous endemie species are still richer in 
the more southern Andine region; the Cichoriaces are below 
those of the adjoining United-States region, although considerably 
more numerous than those of the adjoining Andine, and even of 
the more congenial, though distant, Chilian region; the few Mu- 
tisiaceze are the outlying representatives of a South-American and 
eminently Chilian tribe. A few Old- World, and especially Euro- 
pean aud Mediterranean, races are here represented more strongly 
than in the intermediate United States, or in some cases to their 
exclusion. Adenostyles californica is intermediate, as it were, 
between the two European species. Leucampyz is a close repre- 
sentative of the European Anthemis; Baileya is also nearer to 
some Old- World Chrysanthema than to any American genus ; and 
the Old-World Cnicus has more numerous and much more marked 
Mexican than United-States species. 
It is probable that many additions will be made to the Compo- 
site flora of the Mexican region by future explorations, and more 
especially in well-marked endemie monotypes, which, from the 
severe struggle they have sustained, are generally confined in small 
numbers to limited localities. The above-mentioned Leucampyz, 
so remarkable in its European connexions, is one of the most 
recent discoveries, and only reached me, in fact, at the moment 
when these notes are undergoing the last revision for press. 
2. United-States Region. 
Under this name I would, so far as Composite are con- 
cerned, include the whole of North America east and north of the 
Mexican region. It is true that this may bea combination of two 
floras of separate origin which may appear at first to be very 
distinet, the Rocky-Mountain British-Columbian and Canadian 
flora connected with the Asiatie, and the more strictly American 
flora characterized in Composite by such genera as Helianthus, 
Coreopsis, Rudbeckia, Solidago, Liatris, &c.; but the two are so 
