THE FARMERS' REGISTER. 



463 



Inexhaubiiltle supply lo rrrowin^ plants. The 

 luriiit^hinir of the iwo oilier hiriretfl coiisiiiuen' 

 p;irts ol all plants, uxyizen and hydrouen, is also 

 easy, ami the supply nnlinntcd, as water is coin- 1 

 pcsed of them, and is drawn up hy the roots in' 

 any requisite quantity. Bui siill, a very small i 

 proportion of the waier received hy a plant is 1 

 decomposed by it, and the hydro<j:en and oxyiren 

 assimilated, and made pari ol' its solid substance. : 

 Just as much however is so assimilated as is 

 needed, and as the viijor ol" the fdant can make | 

 used, and appropriaie. The nitroL'en is as car- 1 

 tainly and as bouniilully supplied in diHerent I 

 modes; and the small quantity of the earthy,; 

 alkaline and metallic suhsiances necessary lo ilie! 

 existence of plants are generally present in suffi- 

 cient quantity. 



And here let us glance at a difficulty which at- 

 tends the view thus taken, and which difficulty is- 

 lar greater upon Liebiji's doctrine ol the exclusive 

 supply of' caihon through the leaves, and which 

 he does not attempt to remove. If to plants are 

 offered by the atmosphere unlimited supplies ol 

 carbon, and also of nitrogen (as will be shown 

 presently,) and of hydrogen and oxygen in rain 

 water — and as the earth and air rarely fail to fur- 

 nish enough of the essential earthy or other 

 salts — why is it that exuberant productiveness is 

 not shown on every soil — and that, on the contra- 

 ry, the product of each soil is strictly limited by 

 the measure of its own lertilizing ingredients? 

 We cannot explain this mystery to our own satis- 

 faction. But the nearest approach to ex[)lanation 

 perhaps is, thiit the Ibrce of growth given by the 

 soil enables the plant to seize upon and appropri- 

 ate a certain increased but dtfiniie proponion of 

 the inexhaosiible treasures of the atmosphere. 

 And thus, even though three parts out of (our of 

 the growth may perhaps be due to principles 

 furnished by the atmosphere and by water, still 

 that the benefit tltence derived is nevertheless 

 strictly limited hy, and in proportion to. the mea- 

 sure of the leriiiiiy of the sod. For every addi- 

 tion of" fertility, then, made to the soil, by manur- 

 ing, three times as much effect will be added by 

 the bounty ol nature; and if man giveo nothini:, 

 and removes ail, then the richer bounties of nature 

 are necessarily also withheld. 



But whether furnished altogether tiirough the 

 leaves, or partly through the roots, the carbonic 

 acid is decomposed, and is carbon fixed in the 

 plant, and its oxygen evolved, through the leaves 

 as i;as. 



Hydrogen and oxygen are usually found in 

 plants in the precise proportions in which these 

 two elements Ibrm water. But in some plants the 

 hydrogen is in excess, and more rarely the oxyg^^n. 

 In all cases, the plant decomposes the water need- 

 ed lor combination and assimilation, fixes its ele- 

 ments, and discharges into the air the excess of 

 gas not combined. 



Next will be considered our author's views ol 

 the source and manner of the supply of nitrogen 

 to growing plants. 



Nitrogen forms but a small proportion, but yet 

 an essentia! part of all plants. As it is a large 

 constituent of all animal bodies, so it seems to 

 furnish qualities lo vegetables wtiich are similar 

 to those of animal matter, and is most abundant 

 in the parts of vegetables (as the seeds) which 

 are most nutritious, as food to animals, and as ma- 



nures to other cultivated plants. It Ip a constitu- 

 ent part of the veijetable albumen, and the t-'luien 

 of wheat ; and i.renerally, because of ihe richness 

 it indicates, it is a constituent of plants much 

 more important in proportion to quantity tlian 

 their other clemenis. 



As nitrogen gas is one of the two constituents 

 of the atmosphere, it would seem, at first view, 

 that ihere was the most unlimited and universally 

 pervading supply of this essential and ncliesl of 

 the elements of vegetables. But the laws of na- 

 ture do not permit 'his one of her bounties to be 

 thus directly drawn upon. Liebig says — 



" We have not the slightest reason for believing that 

 the nitrogen of the atmosphere takes part in the pro- 

 ces.-es of assimilation of plants and animals; on the 

 contrary, we know that many plants emit the nitrogen 

 which is absorbed by their roots, either in the gaseous 

 form, or in solution in water. But there are, on the 

 other hand, numerous facts, showing, that the forma- 

 tion in plants of substances containing nitrogen, such 

 as gluten, takes place in proportion to the quantity of 

 this element which is conveyed to their roofs in the 

 state of ammonia, derived fiom the putrefaction of 

 anima! matter." — (p. 126, 7.) 



"Plants, as we l<now, grow perfectly well in pure 

 charcoaf, if supplied at tfie same time with rain-water. 

 Rain-water can contain nitrogen only in two forms, 

 either as dissolved atmospheric air, or as ammonia. 

 Xow, the nitrogen of tne air cannot be made to enter 

 into combination with any element except oxygen, 

 even by employment of the most powerful chemical 

 means." — (p. 126.) 



" Ammonia, too, is capable of undergoing such a 

 multitude of transformations, when in contact with 

 other bodies, that in this respect it is not inferior to 

 water, which possesses the same pi operty in an emi- 

 nent degree. It possesses properties which we do not 

 find in any other compound of nitrogen; when pure, 

 it is extremely soluble in water ; it forms soluble 

 compounds with all the acids ; and when in contact 

 With certain other substances, it completely resigns its 

 character as an alkali, and is capable of assuming the 

 most various and opposite forms." — ^p. 127.) 



"We find this nitrogen in the atmosphere, in rain- 

 water, and in all knids of soils, in the form of ammo- 

 nia, as a product of the decay and putrefaction of 

 preceding generations of animals and vegetables. 

 We find, likewise, that the proportion of azotized 

 matters in pfants is augmented by giving them a larger 

 supply of ammonia conveyed in the form of animal 

 manure. 



" No conclusion can then have a better foundation 

 than this, that it is the ammonia of the atmosphere 

 which furnishes nitrogen to plants." — (p. 146.) 



Thus reasoning that the vast magazine of ni- 

 trogen in the atmosphere, though the only source 

 of the supply, furnishes none directly to plants, 

 I and that they are supplied iinniediaiely only from 

 ■ the soil and through their roots, the author pro- 

 ; ceeds to point out the true sources of ilie necessa- 

 I ry supply. 



" Let us picture to ourselves the condition of a well 

 I cultured farm, so large as to be independent of assist- 

 I aiice from other quarters. On this extent of land 

 i there is a certain quantity of nitrogen contained both 

 t in the corn and fruit wliich it produces, and in the 

 men and animals which feed upon them, and also in 

 their excrements. We shall suppose this quantify 

 I to be known. The land is cultivated without the 

 j importation of any foreign substance containing nitro- 

 ' gen. Now, the products of this farpi must be ex- 

 ; changed every year lor money, and other necessaries 

 I of life, for bodies, therefore, which contain no nitro- 

 1 gen. A certain proportion of nitrogen is exported 



