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Ch. XL.] 



MIGEATTON OF PLANTS. 



383 



The Inminons essay of Auguste De CandoUe on ' Botanical 

 Geograpliy' (1820) presents us with the fruits of his own 

 researches and those of Humboldt^ Brown^ and other eminent 

 botanists, so arranged, that the principal phenomena of the 

 distribution of plants are exhibited in connection with the 

 causes to which they are supposed to be referable."^ ^It 

 it not, perhaps, be difficult,^ observes this writer, Ho find 

 two points, in the United States and in Europe, or in equi- 

 noctial America and Africa, which present all the same 



exam 



same temp 



same height above the sea, a similar soil, an equal dose of 

 humidity ; yet nearly all, perhaps all, the plants in these two 

 similar localities shall be distinct, A certain degree of 

 analogy, indeed, of aspect, and even of structure, might very 

 possibly be discoverable between the plants of the two 

 localities in question ; but the species would in general be 

 difierent. Circumstances, therefore, different from those 

 which now determine the stations^ have had an influence on 

 the habitations of plants/ 



It may be as well to define in this place the technical sense 

 in which the words printed in italics are here used : station 

 indicates the peculiar nature of the locality where each species 

 is accustomed to grow, and has reference to climate, soil, 

 humidity, light, elevation above the sea, and other analogous 

 circumstances j whereas, by habitation is meant a general 

 indication of the country where a plant grows wild. Thus 



mar 



bed of the sea, or a stagnant pool. 



may 



North America, or New Holland 



The study of stations has been styled the topography, that 



of habitations the geography, of botany. The terms thus 



defined, express each a distinct class of ideas, which have 



been often confounded together, and which are equally appli- 

 cable in zoology. 



In farther illustration of the principle above alluded to, 

 that difference of longitude, independently of any influence 

 of temperature, is accompanied by a great, and sometimes a 



-^ Essai El^mentaire de Geographic Eotanique. Extrait du ISme voL du Diet, 

 des Sci. Nat. 1820. 



