Dr. Hugo Mohl, on Lieblg's Organic Chemistry. 87 



of view ; because it is well known that gypsum is most beneficial to 

 leguminous plants. But if its action consisted in fixing ammonia, 

 there is no reason why it should not act beneficially on all plants, 

 especially on Corn. And although L. asserts the latter to be 

 the fact, (Am. d. Chem. u. Pharm. xli. p. 369), yet the farmers, who 

 are pretty good judges in these matters, will not agree with the 

 Professor. If L. explains in a farther part of his work the manuring 

 influence of burnt clay and oxyde of iron by their attraction of 

 ammonia, — an influence which, (he says) could not have been previ- 

 ously understood, it is certainly not to him that the discovery is 

 owing, but to Sprengel, who in his " Doctrine of Manures" has also 

 explained the influence of such substances by their attraction of 

 ammonia. 



Of the fifth chapter, headed " The Inorganic Constituents of 

 Plants," Dr. Mohl says, that Liebig justly rejects the prevailing 

 opinion, that the salts absorbed by plants act merely as stimu- 

 lants, and is right in considering the bases absorbed from the soil as 

 necessary constituents of vegetation. Liebig says, that all plants 

 contain vegetable acids, which become combined with inorganic 

 bases (or organic, formed by the plants themselves) into neutral or 

 acid salts ; — that, considering the constant presence of these acids, 

 we have to infer that they serve some vital purpose, and that 

 their formation constitutes some necessary part of the vital process. 

 Hence, Liebig arrives at the conclusion, that several earthy or 

 alkaline bases can be substituted for each other in the vital process, 

 and that the quantity of the saline bases absorbed by plants depends 

 on the saturating capacity of the acids they contain. This, (says 

 Dr. M„) is the second new and important principle contained in L.'s 

 work. Still, it cannot be considered as perfectly evident, for it 

 is only supported by the analysis of two plants. Whether the 

 enigma which still shrouds the absorption of inorganic substances 

 has been thus solved Dr. M. thinks doubtful. This theory, he says, 

 is, in this respect, one-sided, — that it regards only the basal propor- 

 tion of earth and alkali, and neglects the consideration of the specific 

 proportion, which appertains to such substances in a lesser or 

 greater degree. Many facts shew that the replacing of one base by 

 another is only possible to a certain extent ; that, moreover, the same 



