REGIONS AND AREAS OF DISTRIBUTION. 623 
Chili run also along the western declivity of these intermediate 
Andes. All numbers given in the preceding Tables are in this 
case, therefore, particularly uncertain, notwithstanding the valu- 
able data supplied by Weddell’s * Chloris Andina.’ Accurate as his 
details are, he followed for the limits of his region chiefly altitude, 
which affects what Grisebach terms plant-forms and species, rather 
than genera or other races more indicative of origin, which are 
mostly very different in the Chilian and Columbian Andes. 
In comparing the Composite of this region with those of the 
adjoining Chilian, Brazilian, and especiglly the Mexican region, 
a striking peculiarity is the small number of endemic monoty pes. 
They do not exceed ten ; and not more than half a dozen endemic 
genera of two or three species could be added. The physical 
conditions are not adapted for the preservation of isolated races of 
varied idiosyncracies; they are too generally uniform to afford the 
necessary protection against luxuriant races which can freely 
range over large districts. As in the temperate and mountain 
regions of the north, this comparative uniformity of physical con- 
ditions has given at once a wide range to species and a large 
average of species to the characteristic genera. These compara- 
tively uniform conditions are also evidently such as to favour the 
development of Composite; and, moreover, the region itself is 
probably one which was very early inhabited by the order. The 
total number now known, very nearly the same as that of the 
Brazilian region, far exceeds that of any other American one 
except the Mexican. A few of the endemic or nearly endemic 
genera (such as Astemma, some of the Mutisiacez, dic.) may be 
supposed to bear evidences of great antiquity; others appear to be 
in the height of prosperity and luxuriance ; and the region exhibits 
more arborescent Composite than any other, except insular ones. 
Among the characteristic tribes of the Andine region the 
heterochromous Asteroidez, the Senecionidez, and Eupatoriacee, 
which take a second place in the Mexican region, may be here 
placed in the first rank on a par with the Helianthoidex ; the 
Mexican Helenioidez and homochromous Asteroidex arereduced to 
very few species; and the only endemic races of any higher value are 
a small Andine section of Chrysothamnus* (four species), Cacosmia 
(three species), which is almost as near to Calea as to its technical 
cotribuals, and Schizotrichia, a single species as yet, perhaps, 
imperfectly known. Vernoniacez, rather more numerous than in 
* Sincethis paper has been in the printer's hands it has been pointed out to me by 
Asa Gray that De Candolle's name Bigelovia has the right of priority for this genus, 
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