Schow's Essay on Botanical Geography. 163 



he determined the relations of plants to their elevation by the help of the 

 barometer, and inquired into the medium temperature which individual 

 plants required. Decandolle in his " Flore' Francaise," divided France 

 into several regions, according to the difference of vegetation, and treated 

 of the influence of difference of elevation on vegetation. At last appear- 

 ed Humboldt in 1807, with his " Essai sur la geographie des Plantes," 

 and " Tableau des regions Equinoctiales." The first was at the most but a 

 very loose sketch, neither was the latter at all a complete comparison be- 

 tween climate and vegetation ; but as he elevated the most interesting of 

 sciences, — as he, in a striking manner, connected so many physical pheno- 

 mena, which previously had been handled separately, — so he excited a ge- 

 neral interest for these inquiries, and this work, therefore, decidedly forms 

 an epoch in the science. His " Tableau de la Nature" co-operated also 

 to produce this effect. Next followed Wahlen berg's " Flora Lapponica," 

 a classical work, which advanced the whole of the geography of plants. 

 This author was doubtless the first who clearly showed that the an- 

 nual medium temperature is not a sure scale for vegetation, but that 

 attention must also be paid to the distribution of heat in the differ- 

 ent parts of the year. He was the first who instituted an ample compa- 

 rison between vegetation in all its relations ; and lastly, he was the first, 

 who, in any perfection, showed the mutual relations of families of plants, 

 and it is only to be lamented, that in this he preferred the Linnaan to Jus- 

 sieu's natural families. The same author his since published two equally 

 important works, on the north of Switzerland, and the Carpathian Moun- 

 tains ; he has proceeded in them on the same principles as in the " Flora 

 Lappwica ;" corrected several of them, for example, his theory on the 

 temperature of the earth as a scale for vegetation, and given his views 

 greater extension, by comparing Sweden with Switzerland, and both 

 with the Carpathians. In a treatise in " Magwzin der Gesellschaft natur- 

 forschenJer Freunde," he has made remarks on the difference between the 

 vegetation of the coast, and the inland, (littoral and continental vegeta- 

 tion.) Engelhardt and Parrot have given in their travels some infor- 

 mation concerning the planto-geographic relations of Caucasus. In 1814, 

 R. Brown published his " General Remarks on the botany of Terra- Austra- 

 lis." In this treatise, the relations of the families of plants are discussed 

 with great acuteness and science ; the author's deep study of the natural 

 families, and the many opportunities he had for comparing the plants of 

 New Holland, with those of other parts of the globe, ought to give this 

 work a high degree of perfection. On the other hand, he has not so much 

 as touched upon the influence of climate on vegetation. 



Hitherto, with the exception of single hints in R. Brown's work, and 

 Treviranus's imperfect essay, botanists stopped at single countries, and did 

 not venture to deduce results for the whole of the globe. This step Hum* 

 Imlilt made in 1815, in the introduction to the botanical part of his travels; 

 and although, from the plan of the introduction, the representation of the 

 general laws must be disjointed, it could not but lead to general views, 

 and thus, as well as by its richness in ideas, again make an epoch in the 



