REGIONS AND AREAS OF DISTRIBUTION. 543 
the other genus, Homogyne, is one of the Tussilago group, chiefly 
Europso-Asiatie, but also extending into North America, where, 
indeed, the section Nardosmia of Petasites is, perhaps, the nearest 
connexion of the European Homogyne. To these two European 
genera, not extending into Asia, might perhaps be added Berardia ; 
but, although limited to the Alps of Dauphiné, that plant is so 
essentially Mediterranean in its character that it seems to be 
more appropriately regarded as an outlying member of the Medi- 
terranean flora. 
After deducting a few Mediterranean species which have ex- 
tended northwards over the temperate portions of our Europso- 
Asiatic region, and perhaps a few endemic species which Mediter- 
ranean genera have there established, the great majority of the 
genera are essentially Asiatic—many of them exclusively so, others 
gradually diminishing in species as they extend westward; and 
some of them, as shown in Table 5, are also represented by 
identical species or by congeners in North America. All these, 
together with the two above-mentioned European genera, must 
probably have had their origin in the flora which has often been 
commented on as having once extended over the greater part of the 
higher northern region of the globe, and of which we have now 
sometimes detached remnants preserved in limited localities often 
at great distances from each other, sometimes thriving descendants 
which have multiplied in species and individuals over a large 
portion of the area. : 
To these probably very ancient denizens of the region must be 
added in its eastern portion a few genera of one or two species 
each, Myripnois, Pertya, Macroclinidium, which, with the northern 
species of Ainsliea and perhaps Leucomeris and Catamixis, are the 
northern representatives of the essentially southern tribe of Mu- 
tisiaceæ. These, with Gynura, Tricholepis, and other southern 
genera of other tribes, are instances of that interchange of 
northern and southern races in eastern Asia to which I have 
above alluded, the return being made in the few species of 
Eupatorium, Boltonia, Anaphalis, Chrysanthemum, Artemisia, 
Saussurea, &c., which, from the Europeo-Asiatic region, have 
in its eastern portion protruded southward to within the tropics, 
one, Saussurea, crossing over even into Australia. 
I can find no traces in Composite of that strictly western flora 
exemplified in Lobelia, Erica, Ulex, and other Genistem, &e., 
owing possibly to the supposed less ancient origin of the order, 
LINN. JOURN.—BOTANY, VOL. XIII. 2Q 
