on the Surface of the Glohe^ ^61 



A temperature constantly humid and warm, such as that of 

 the equinoctial countries, maintained by the rays of a burning 

 sun, and the emanations of a soil watered by the vicinity of 

 large rivers and lakes, gives to vegetation that vigour which as- 

 tonishes in those magnificent vegetables peculiar to those cli- 

 mates. Another form of plants is seen in those countries which 

 are exposed to the alternations of cold and warm seasons ; it is 

 more equal upon the sea-coasts, where the temperature is less va- 

 riable ; but the plants assume another aspect upon the high moun- 

 tains, where dry and cold winds frequently blow ; they vary lit- 

 tle in the fresh-waters, or in those of the sea ; being there placed 

 in a medium less subject to the inclemencies of the atmosphere. 

 The intensity and duration of the light, the long and humid 

 nights, occasion as many different modifications in the vegetable 

 forms. Nature has also so fixed the station of plants, that the 

 dwarf and creeping willows never descend from the summit of 

 their mountains to associate with the osier willows, upon the 

 banks of our brooks ; and the primulae, which decorate the green 

 swards of the Alps, cannot mingle with those of our meadows. 



From these considerati©ns has arisen the idea of a botanical 

 geography, in which the plants are distributed by groups, which 

 have each their determinate height, their climate, and their li- 

 mits. Several naturalists have directed their attention to this 

 sort of observations, but no one has carried them so far as M. 

 de Humboldt, who has published memoirs of great interest up- 

 on this subject. From the observations of this learned traveller, 

 and those partly made before him, we see the cruciform plants 

 and the umbelliferae disappear, almost entirely, in the plains of 

 the torrid zone ; while this zone is the abode of palms, tree- 

 ferns, gigantic gramineae, and parasitic orchideae. In the tem- 

 perate zones grow abundantly the malvaceae, the labiatae, the 

 compositae and caryophylleae, which are very rare under the 

 equator. The coniferae, and a great number of amentaceous 

 trees, belong to the boreal regions. There are other families 

 which recur, in almost all the countries of the globe, such as the 

 gramineae and the cyperaceae, but under different forms, accord- 

 ing to the temperatures. Some of them nearly rival the palms 

 in size, such as the bamboos, &c. ; others form but a short and 

 tufted sward. My limits not permitting me to enter farther in-. 



