ASSIMILATION OF NITROGEN. 



33 



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 azotised components of the 

 branches, blossoms, and leaves, as well as 

 of tnose which contain no azote or nitrogen. 

 In proportion as the developement 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 

 cultivation of grain, and the vegetables 

 which serve for fodder to cattle, is the most 

 convincing proof that the nitrogen of vege- 

 tables is derived from ammonia. The 

 quantity of gluten in wheat, rye, and bar- 

 ley, 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 ob- 

 tained 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 Bous- 

 singault. 17.3 per cent, of gluten; that of 

 wheat grown in the " Jardin des Plantes" 

 26.7, and that of winter wheat 3.33 per cent. 

 Such great differences must be owing to 

 some cause, and this we find in the diffe- 

 rent methods of cultivation. An increase of 

 animal manure gives rise not only to an in- 

 crease in the number of seeds, but also to a 

 most remarkable difference in the proportion 

 of the substances containing nitrogen, such 

 as the gluten which they contain. 



'Animal manure, in as far as regards the 

 assimilation of nitrogen, acts only by the 

 formation of ammonia. One hundred parts 

 of wheat grown on a soil manured with 

 cow-dung (a manure containing the smallest 

 quantity of" nitrogen.) afforded only 11.95 

 parts of gluten, and 64.34 parts of amylin, 

 or starch ; whilst the same quantity, grown 

 on a soil manured with human urine, yielded 

 the maximum of gluten, namely 35.1 per 

 cent. Putrefied urine contains nitrogen in 

 the forms of carbonate, phosphate, and lac- 

 tate of ammonia, and in no other form than 

 that of ammomacal salts. 



" Putrid urine is employed in Flanders as 

 a manure with the best results. During the 

 putrefaction of urine, ammoniacal salts are 

 formed in large quantity, it may be said ex- 

 clusively; for under the influence of heat 

 and moisture, urea, the most prominent in- 

 gredient of the urine, is converted into car- 

 bonate of ammonia. The barren soil on the 

 coast of Peru is rendered fertile by means of 

 a manure called Guano, which is collected 

 from several islands in the South Sea.* It 

 is sufficient to add a small quantity of guano 



* The guano, which forms a stratum several 

 feet in thickness upon the surface of these islands, 

 consists of the putrid excrements of innumerable 



P 



'to a soil, which consists only of sand and 

 ' clay, in order to procure the richest crop of 

 maize. The soil itself does not contain the 

 smallest particle of organic matter, and the 

 manure employed is formed only of urate, 

 phospliate, oxalate, and carbonate of ammonia, 

 together with a few earthy salts."* 



Ammonia, therefore, must have yielded 

 the nitrogen to these plants. Gluten is ob- 

 tained not only from corn, but also from 

 grapes and other plants ; but that extracted 

 from the grapes is called vegetable albumen, 

 although it is identical in composition and 

 properties with the ordinary gluten. 



It is ammonia which yields nitrogen to 

 the vegetable albumen, the principal con- 

 stituent of plants ; and it must be ammonia 

 which forms the red and blue colouring 

 matters of flowers. Nitrogen is not pre- 

 sented to wild plants in any other form ca- 

 pable of assimilation. Ammonia, by its 

 transformation, furnishes nitric acid to the 

 tobacco plant, sun-flower, Chenopodium, and 

 Borago ojficinalis, when they grow in a 

 soil completely free from nitre. Nitrates 

 are necessary constituents of these plants, 

 which thrive only when ammonia is present 

 in large quantity, and when they are also 

 subject to the influence of the direct rays of 

 the sun, an influence necessary to effect the 

 disengagement within their stem and leaves 

 of the oxygen, which shall unite with the 

 ammonia to form nitric acid. 



The urine of men and of carnivorous 

 animals contains a large quantity of nitrogen, 

 partly in the form of phosphates, partly as 

 urea. Urea is converted during putrefac- 

 tion into carbonate of ammonia, that is to 

 say, it takes the form of the very salt which 

 occurs in rain-water. Human urine is the 

 most powerful manure for all vegetables 

 containing nitrogen; that of horses and 

 horned cattle contains less of this element, 

 but infinitely more than the solid excrements 

 of these animals. In addition to urea, the 

 urine of herbivorous animals contains hip- 

 puric acid which is decomposed during pu 

 [refaction into benzoic acid and ammonia. 

 The latter enters into the composition of the 

 luten, but the benzoic acid often remains 

 unchanged: for example, in the Jlntlwxan 

 thum odoratum. 



The solid excrements of animals contain 

 omparatively very little nitrogen, but this 

 could not be otherwise. The food taken by 

 animals supports them only in so far as it 

 offers elements for assimilation to the various 

 organs which they may require fcx their 

 ncrease or renewal. Corn, grass, ami all 

 slants, without exception, contain azotised 

 substances. The quantity of food which 

 animals take for their nourishment, dimi- 

 nishes or increases in the same proportion 

 as it contains more or less of the substances 

 containing nitrogen. A horse may be kept 



sea fowl that remain on them during the breeding 

 season. See the Chapter on Manures.) 



* Boussingault, Ann. de Ch. et de Phys. Lxv. p. 

 319. 



