Reviews. — Liebig''s Organic Chemistry. 351 



however, has nothing to do with the geographical distribution 

 of plants, but is a theory to account for a certain suscepti- 

 bility of particular trees and plants to particular soils. 



How does it happen that wheat does not flourish on a sandy soil, 

 and that a calcareous soil is also unsuitable for its growth, unless it 

 be mixed with a considerable quantity of clay? It is because these 

 soils do not contain alkalies in sufficient quantity, the growth of 

 wheat being arrested by this circumstance, even should all other sub- 

 stances be presented in abundance. 



It is not mere accident that only trees of the fir tribe grow on the 

 sandstone and limestone of the Carpathian mountains and the Jura, 

 whilst we find on soils of gneiss, mica-slate, and granite in Bavaria, 

 of clinkstone on the Rhone, of basalt in Vogelsberge, and of clay- 

 slate on the Rhine and Eifel, the finest forests of other trees which 

 cannot be produced on the sandy or calcareous soils upon which 

 pines thrive. It is explained by the fact, that trees, the leaves of 

 which are renewed annually, require for their leaves six to ten times 

 more alkalies than the fir-tree or pine, and hence, when they are 

 placed in soils in which alkalies are contained in very small quantity, 

 do not attain maturity. When we see such trees growing on a sandy 

 or calcareous soil, — the red beech, the service-tree, and the wild- 

 cherry, for example, thriving luxuriantly on limestone, we may be 

 assured that alkalies are present in the soil, for they are necessary to 

 their existence. Can we, then, regard it as remarkable, that such 

 trees should thrive in America, on those spots on which forests of 

 pines which have grown and collected alkalies for centuries, have 

 been burnt, and to which the alkalies are thus at once restored; or 

 that the Spartium scoparium, Erysimum lalifolium, Blilum capita- 

 turn, Senecio viscosus, plants remarkable for the quantity of alkalies 

 contained in their ashes, should grow with the greatest luxuriance on 

 the localities of conflagrations. 



Wheat will not grow on a soil which has produced wormwood, 

 and, vice versa, wormwood does not thrive where wheat has grown, 

 because they are mutually prejudicial by appropriating the alkalies 

 of the soil. 



In chapter VIIT. we are presented with the philosophical 

 views of interchange of crops, and of manure. From this, 

 we briefly gather, that by rotation of crops, certain alkalies 

 and other principles are restored to the soil, of which it had 

 been deprived by the previous culture. This is a different 

 process from the one eflected by the fallow crop system, as in 

 that. 



The land is exposed to the progressive disintegration by means of 

 the influence of the atmosphere, for the purpose of rendering a cer- 

 tain quantity of alkalies capable of being appropriated by plants. 



Now, it is evident, that the careful tillinji of fallow land must in- 

 crease and accelerate this disintegration. For the j)ur|)ose of agri- 

 culture, it is quite iudifl:crent, whether the land is covered with 



