SCHULTZENSTEIN — NUTRITIVE CONSTITUENTS OP WATER. 123 



bined with carbon, hydrogen, and oxygen, in the form of geic acid, 

 crenic acid, humate of ammonia, which exist in vegetable nutri- 

 ment thus formed. This nutriment is therefore a single sub- 

 stance, whose different constituents are by no means gathered 

 together from so many quarters as Liebig supposes. Carbonate 

 of ammonia is never assimilated by plants. 



Another form in which nitrogen enters into plants is nitric 

 acid, which is widely diffused in the soil, and generally combined 

 with clay, magnesia, lime, potash or soda — in many places so 

 abundantly that in Egypt, Tibet, the East Indies, Italy, France, 

 Spain, Hungary, and America the saltpetre effloresces and is 

 easily collected. Nitric acid is formed by the oxidation of the 

 ammonia, which is produced by the combination of the hydrogen 

 eliminated from the soil with the nitrogen of the air. In con- 

 sequence nitric acid, nitrate of lime, and saltpetre always exist in 

 humous clay and limestone soils. The nitric acid is assimilated 

 by the plants in the same way as other acids and humic acids, 

 since the oxygen is exhaled in light, the nitrogen retained (Entd. 

 der Pnanzennahrung, p. 120). 



Saussure's view, reproduced by Liebig, that the nitrogen of plants 

 originates from the carbonate of ammonia in the air, and that all 

 manures operate only by the formation of carbonate of ammonia, 

 is therefore altogether erroneous, and can only lead to great errors 

 in practical farming. Liebig' s theory of manures runs throughout 

 on the evolution of carbonate of ammonia from the dung, and the 

 addition of gypsum in order to its fixation. It is supposed that 

 the effect of gypsum depends only on the fixation of ammonia. 

 It is plain, from practical experiments on the effect of gypsum in 

 Horticulture and Agriculture, that this view is altogether wrong. 

 Gypsum promotes the growth of the leaves and stems only of 

 leguminous plants, as clover and peas, but never the blossoming 

 and ripening of the fruit. On the contrary, gypsum, in consequence 

 of the continued luxuriant growth, hinders the formation and 

 ripening of the fruit, and therefore is very injurious in the cultiva- 

 tion of peas in fields, since these plants, when strewed with 

 gypsum, continue green for a long time and produce with difficulty 

 only a little seed. We have also shown that no neutral salts, and 

 therefore neither gypsum nor sulphate of ammonia, cau be de- 

 composed and assimilated by plants. 



Ammoniacal, especially nitrogenous matters, have precisely the 

 contrary effect on vegetation : they promote, that is, the blossom- 

 ing and formation of fruit, and impede the growth of leaves and 



