252 THE GEOGRAPHY 



them in a peculiar condition. If to these three classes of 

 Air, Water, and Earth-plants, we add one more, namely, 

 the true Parasites, which, like our Dodder, draw their 

 organized nutriment from other plants, we have obtained 

 the principal divisions of stations. Next come the sub- 

 divisions, which are determined by the matters which the 

 water holds in solution and thus conveys to the plant. I 

 have already decided that carbonic acid and salts of 

 ammonia must always be present among these, to render 

 vegetation possible. Perhaps even here the more or less 

 of these two ingredients and their relation to each other, 

 may make a distinction which we are not yet in a position 

 to estimate. The relations of the inorganic constituents, 

 the salts dissolved in water, to the plants, are more evident 

 to us. Science has in this very point gone astray in the 

 most varied and opposite directions. So late as the com- 

 mencement of the present century, there were men who 

 asserted, that plants could themselves form all their organic 

 and inorganic constituents out of air and distilled water. 

 Superficial experiments, which yet were crowned by 

 academicians devoid of judgment, fantastic prating, instead 

 of logical accuracy of thought, allowed such distorted views 

 to obtain a temporary worth among a number of naturalists. 

 Subsequently, the error was in the other extreme, for there 

 was an inclination to ascribe a peculiar Flora to each 

 geognostic formation ; and this last error even yet haunts 

 the agricultural doctrines which would determine the good- 

 ness and intrinsic worth of a soil by the plants that grow upon 

 it. Truth here lies between the two extremes. I have 

 already had opportunity to demonstrate what very different 

 amounts and kinds of inorganic matters plants demand in 

 their vegetation. When we find that the ashes of Lucerne, 

 of Tobacco, of Clover, contain more than 20 per cent, of 



