94 SOURCE AND ASSIMILATION OF NITROGEN. 



juice possesses the same characters as the solution 

 of such a salt in water; it acquires, namely, an 

 acid reaction during evaporation, in consequence of 

 the neutral salt being converted by loss of ammonia 

 into an acid salt. The free acid which is thus 

 formed is a source of loss to the manufacturers of 

 sugar from beet-root, by changing a part of the 

 sugar into uncrystallizable grape sugar and syrup. 



The products of the distillation of flowers, herbs, 

 and roots, with water, and all extracts of plants 

 made for medicinal purposes, contain ammonia. The 

 unripe, transparent, and gelatinous pulp of the al- 

 mond and peach emit much ammonia when treated 

 with alkalies. (Robiquet.) The juice of the fresh 

 tobacco leaf contains ammoniacal salts. The water 

 which exudes from a cut vine, when evaporated 

 with a few drops of muriatic acid, also yields a 

 gummy, deliquescent mass, which evolves much am- 

 monia on the addition of lime. Ammonia exists in 

 every part of plants, in the roots (as in beet-root), 

 in the stem (of the maple-tree), and in all blossoms 

 and fruit in an unripe condition. 



The juices of the maple and birch contain both 

 sugar and ammonia, and therefore afford all the con- 

 ditions necessary for the formation of the azotized 

 components of the branches, blossoms, and leaves, 

 as well as of those which contain no azote or nitro- 

 gen. In proportion as the development of those 

 parts advances, the ammonia diminishes in quantity, 

 and when they are fully formed, the tree yields no 

 more juice. 



The employment of animal manure in the cultiva- 

 tion of grain, and the vegetables which serve for 

 fodder to cattle, is the most convincing proof that 

 the nitrogen of vegetables is derived from ammonia. 

 The quantity of gluten in wheat, rye, and barley, is 

 very different ; these kinds of grain also, even when 

 ripe, contain this compound of nitrogen in very 

 different proportions. Proust found French wheat 

 to contain 12*5 per cent, of gluten 3 Vogel found that 



