REGIONS AND AREAS OF DISTRIBUTION. 495 
differentiated should any change in physical conditions tend to 
isolate them. It will be observed that these American species 
supposed to be prehistorically established in the Old World are 
in their present distribution mostly rather of an Asiatic and 
chiefly Eastern than of an African character; and this, taken in 
conjunction with the Wedelia (Stemmodon), Melampodium, and 
some other E.-Asiatic types of the first list, and with many 
instances that might be taken from other orders, might induce a 
belief that, as far as plants are concerned, the connexion or 
communication (whatever may have been its nature) between 
America and east tropical Asia was of an antiquity less remote 
than that between tropical America and Africa. 
Table 5. Extratropical Northern connexion between America and 
the Old World as indicated by identical or nearly allied Species, 
Sections, or Genera. 
This Table includes all the genera whose connecting sections or. 
species are northern and extratropical, although some of them 
may extend into the tropics in one or both divisions of the globe, 
but generally with a greater divergence in character as well 
as in geographical position than in the north. Some may reappear 
in the south, and even may there cross again from the New to 
the Old World (e. g. Centaurea), and may therefore be repeated 
in Table 7, although the primary connexion was probably northern. 
Genera. | American races. Common races. | Old-World races. 
About 24 North-Ameri- 
ean species, but about 
400 more dispersed over 
Central and South 
EUPATORIUM. 
or 3 extending west- 
ward to the Mediterra- 
nean region and Europe 
generally, and lin east 
tropical Africa; all 
North-American ones | 
nearer to the Old- | 
World forms than to | 
America. the mass of American | 
None; but some of the 7 or 8 Asiatic species, 2 | 
ones. i 
| elosely allied to each 
| other and to some 
| North-American 
5 | forms. 
Connexions ...| Several American genera |... eene ! None very near. 
ADENOSTYLES | 1 Californian species. None; but the American | 2 European species. 
species nearer to one of | 
i the European than | 
: | they are to each other. | 
Connexions | None very near; bub|.—————————— ar | None nearer than Eupa- 
Brickellia perhaps | torium, a more remote 
nearer than Eupato- | one with some Senecio- 
| rium. |  nidege. 
SOLIDAGO .... Nearly 80 species, chiefly | S. virga-aurea, L. | None besidesthe common 
North-American ; a few one and a few colonists. 
West-American or 
: | southern extratropical. | 
Connexions ...| Several North or West |.......... cen None in the north; a 
LINN. JOURN.— BOTANY, VOL. XIII. 
| American or south ex- 
| tratropical genera. 
few extratropical 
| South-African genera. 
2N 
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