of vegetable Forms. 451 
do not follow the same laws with the mosses and the lichens; 
The former, in particular, exhibit very few species universally to 
be found; and the examples cited are frequently doubtful. As 
to the phanerogamous plants (with the exception o/ the rhizo- 
phora, the avicennia, and some other littoral plants), the law of 
Buffon seems to he exact with respect to the species furnished 
with two cotyledons. It is absolutely false, although it has been 
often affirmed, that the ridges of the cordilleras of Peru, the 
climate 6f which has some analogy with the climate of France 
or Sweden, produce similar plants. The oaks, the pines, the 
yews, the ranunculi, the rose-trees, the alchemilla, the valerians, 
the stellaria, the draba of the Peruvian and Mexican Andes, have 
nearly the same physiognomy with the species of the same ge- 
nera of North America, Siberia, or Europe. But all these al 
pine plants of the Cordilleras, without excepting one among 
three or four thousand which we have examined, differ specifi- 
cally from the analegous species of the temperate zone of the old 
continent. In general, in that part of America situated between 
the tropics, the monocotyledontal plants alone, and among the 
latter almost solely the cyperacee and the graminez, are com- 
ion to the two worlds. These two families form an exception 
to the general law which we are here examining,—a law which is 
so important for the history of the catastrophes of our planet, 
and according to which the organized beings of the equinoctial 
regions differ essentially in the two continents. I have given in 
nity Prolegomena a precise catalogue of those monocotyledontal 
plants common to the shores of the Oronoko, Germany, and the 
East Indies. Their number does not exceed 20 or 24 species, 
among which it is sufficient to cite the cyperus mucronatus, 
c. hydra, hypzlyptum argenteum, poa eragrostis, andropogon, 
allioni, &c. 
In North America placed beyond the tropics, we find nearly 
one-seventh of monocotyledontal and dicotyledontal plants com- 
mon to the two continents. Of 2900 phanerogamous species 
collected in the New Flora of Pursch, 390 are European. It is 
true that we may hazard some doubts, as well with respect to 
the number of the plants which have accompanied Europeans 
from one hemisphere to the other, as upon those which, when 
better examined, will be recognised subsequently as new species: 
but it is impossible that this. state of uncertainty should extend 
to all; and it is to be presumed that, even after a careful exami- 
nation, the number of the species common to the temperate 
zones of the two worlds will still remain very considerably ana- 
logous. Mr. Brown recently undertook some researches on the 
plants of New Holland. A twenty-eighth part of all the mono- 
cotyledons hitherto found in the austral continent are common 
Ff 2 to 
