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Liebig says : — " That the greater quantity of azotized 
" substances which are used as manures, the greater the 
" quantity of produce ; and that the chief art of agriculture 
" depends upon the collection and preservation of those 
" manures which contain ammonia in the greatest quantity. 
" Now liquid animal excretions, if suffered to undergo the 
" process of putrefaction, contain the greatest quantity of 
" ammonia, and in that form of salts which has lost its 
" volatility ; and when presented to the growing plants in this 
" condition, they are the most valuable of all manures, and 
" not the smallest portion is lost to the plants. It is all 
" dissolved by water, and imbibed by the roots." 
Nitrogen, derived from ammonia or from nitric acid, is so 
essential to vegetable life, that it has been termed the moving 
agents which acts under the influence of the living principle 
of the plant, moulding into shape the other elements 
Professor Johnston has beautifully pointed out the design 
intended by the presence of nitrogen in the germination of 
seeds, by the formation of diastase, (as named by Payen and 
Persoz,) by which the farina of the grain is converted first 
into gum and afterwards into sugar ; but the use of nitrogen 
in the seed is not limited to this process, as intimated by the 
Professor, for by the elaborate experiments performed by 
Rigg, and published in the Philosophical Transactions, Part 
II. for 1838, it was proved that nitrogen predominates, when 
compared with the other part of the seed, in the germ and 
cotyledons of beans, peas, barley, and wheat, a large excess 
of nitrogen being invariably indicated in the germ. So that 
in the seed it possesses other uses besides the conversion of 
the starch into sugar ; indeed, one part of diastase has the 
power to convert 2,000 parts of starch into sugar. Rigg 
found, moreover, nitrogen not only abounding in the germ, 
but that the chemical constitution of the rootlets, before the 
plumula extends the whole length of the seeds, as in the 
