PhUosophiccd Character of DecandoUe. 229 



Plants, and likewise, in the Memoires de la Societe d'Arcueil, 

 his masterly dissertation on the Distribution of Heat through- 

 out the Globe, M. Decandolle contributed to the same work, a 

 general sketch of the subject of Botanical Geography, which, 

 in an expanded and corrected form, has been inserted in the 

 Dictionnaire des Sciences Naturelles, by Levrault, published 

 in 1820. 



In this essay, he first considers in detail, the influence of 

 the different agents which affect the growth of plants, such 

 as temperature, light, humidity, the soil, and the atmosphere 

 — he then points out the several stations or situations in a 

 particular country which certain plants affect, as, for example, 

 the neighbourhood of the sea, marshes, cultivated land, rocks, 

 sand, forests, the dwellings of man, &c. — and, lastly, he passes 

 in review the distribution of the different tribes of plants over 

 the various regions of the globe, such as the tropical, the 

 temperate, and the frigid zones. 



Having thus, both from theory and from observation, estimated 

 the degree of influence exerted by external agents upon the 

 distribution of plants, he is in a condition to consider the in- 

 teresting problem, as to whether the limited range of country, 

 to which in a state of nature each species would appear to be 

 confined, is referable solely to the above circumstances. 



If the affirmative of this proposition be granted, we have 

 then the choice of several suppositions, for either we may sup- 

 pose, that plants were at first scattered indiscriminately over 

 the whole globe, or, as Linnaeus imagined, that they spread 

 themselves from some one central spot in different directions, 

 according as the conditions were favourable or otherwise ; 

 or, if we chose to give in to the Lamarckian view of the 

 gradual progression of more perfect from less perfect forms, we 

 might imagine each plant to be generated at or near the spot 

 where it is found, owing to the influence of external causes 

 operating upon matter endued with some principle of vita- 

 lity. 



But if the negative must be concluded — if, after making 

 all allowance for circumstances, there remains something yet 

 to be explained with respect to the geographical distribution 

 of vegetables, we are then led to the conclusion, that each 



VOL. xxxiv. NO. Lxvrir. — apkil 1843. q 



