459 Laws observed in the Distribution 
rhododendrons, and the gramineous plants. On the contrary, 
the labiate, the rubiacew, the malvacee, and the euphorbiacese 
then become as rare as they are in Lapland. But this analogy 
is not supported in the ferns and the composite plants. The 
latter abound on the Andes, whereas the former gradually dis- 
appear when they rise above 1890 fathoms in height. Thus the 
climate of the Andes resembles that of northern Europe only 
with respect to the mean temperature of the year. The repar~- 
tition of heat into the different seasons is entirely different, and 
powerfully influences the phenomena: of vegetation. In general, 
the forms which prevail among the Alpine plants are, according 
to my researches, UNDER THE TORRID ZONE, the graminee 
(e2gopogon, podosemum, deyeuxia, avena) ; the composite 
(culvitium, espeletia, aster, baccharis); and the caryophyllee 
(arenaria, stellaria). UNDER THE TEMPERATE ZONE, the com- 
posite (senecio, leontodon, aster) ; the caryophyllee (ceras- 
tium, cherleria, silene); and the crucifere (draba, lepidium). 
UNDER THE FROZEN ZONE, the caryophyllee (stellaria, alsine) ; 
the ericinee@ (andromeda) and the ranunculacee. 
These researches into the law of the distribution of forms, na- 
turally lead to the question whether there exist plants common 
to both continents? a question which inspires the more interest, 
as it belongs to one of the most important problems in Zoonomia. 
It has been long known, and it is one of the most interesting 
results from the geography of animals, that no quadruped, no 
terrestrial bird, and, as appears from the researches of M. La- 
treille, almost no insect, is common to the equatorial regions of 
the two worlds. M. Cuvier is convinced by precise inquiries 
that this rule applies even to reptiles. He has ascertained that 
the true boa constrictor is peculiar to America, and that the 
boas of the old continent were pytons. As to the regions beyond 
the tropics, Buffon has multiplied beyond measure the number 
of the animals common to America, to Europe, and the north of 
Asia. We are assured that the bison, tHe stag, and the goat of 
America, the rabbit and the musk rat, the bear, &c. &c. are 
species entirely different from those of Europe, although Buffon 
had affirmed the contrary. There remain only the glutton, the 
wolf, the white bear, the red fox, perhaps also the elau, which 
have not characters sufficient to entitle them to be specific. 
Among the plants, we must distinguish between the agame and 
the cotyledonez ; and by considering the latter between the mo- 
nocotylodens and the dicotyledons. There remains no doubt 
that many of the mosses and lichens are to be found at once in 
equinoctial America and in Europe: our herbals show this. But 
the case is not the same with the vascular agame as with the 
agamee of acellular texture. The ferns and the lycopodiacex 
do 
