80 SOURCE AND ASSIMILATION 



deliquescent mass, which evolves much ammonia 

 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 

 conditions necessary for the formation of the azo- 

 tised components of the branches, blossoms, and 

 leaves, as well as of those which contain no azote 

 or nitrogen. 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 culti- 

 vation 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; Vogel 

 found that the Bavarian contained 24 per cent. ; 

 Davy obtained 19 per cent, from winter, and 24 

 from summer wheat ; from Sicilian 21, and from 

 Barbary wheat 19 per cent. The meal of Alsace 

 wheat contains, according to Boussingault, 17.3 per 

 cent, of gluten ; that of wheat grown in the " Jar- 

 din des Plantes" 26.7, and that of winter wheat 



