OF PLANTS. 241 



same plants, for every one of these exhibits in its own way, 

 both kinds of distribution. Side by side, lie a soluble and 

 an insoluble problem, the former soluble because the ques- 

 tion can be stated definitely, and has been stated by A. von 

 Humboldt, namely the Dependance of the Distribution 

 of Plants on the Physical Conditions of the Earth the 

 second insoluble, because no definite proposition can be laid 

 down which the inquirer may apply himself to elucidate. 

 In regard to the first, therefore, we can bring the collected 

 facts into explanatory coherence ; from the second point of 

 view, on the contrary, we obtain nothing but an aggregate 

 of incoherent facts, at present incapable of any explanation, 

 but perhaps having even on that account so much the 

 greater claims on our interest. With permission I shall 

 slightly sketch the conditions of plants on the earth's 

 surface in both relations ; and in conclusion, delineate with 

 somewhat greater completeness, as it were as a more fully 

 perfected example, the distribution of the most important 

 nutrient and economic plants upon the globe. 



THE DEPENDANCE OF THE DISTRIBUTION OF PLANTS ON 

 PHYSICAL CONDITIONS. 



We must here take our departure from the smallest, 

 most limited circle, in the intention to spread ourselves at 

 last over the whole earth. The origin of the compre- 

 hensive Geography of Plants was no greater thing than 

 the daily question : Where does the plant grow ? And 

 every Botanist treats, more or less superficially, a chapter 

 of the so-called habitations, the place of growth and 

 the native country of the plant. Through these small 

 beginnings of Science have light and order gradually come 



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