CIO 



FARMERS' REGISTER 



[No. 10 



into plants only in a state of solution, or of extreme 

 division in water. Healthy plants absorb from 

 preference those salts that are most congenial to 

 them; but if waters be charged with salts unstated 

 to their natures, they absorb the fluid and reject 

 the sails till the water becomes thickened by them. 

 There are some salts which enter naturally into 

 the composition of certain plants; the pellitory and 

 nettle, lor instance, which grow upon the borders 

 of the sea, contain muriate or sulphate of soda; 

 these vegetables, transported into olhersoils, afford 

 no vestige of these salts, and their growth is vigo- 

 rous. M. le Marquis de Bullion has proved that 

 the tumsol, raised in earth containing no nitre, 

 does not, upon analysis, afford a vestige of any; 

 but that plants of the same kind, raised in the 

 came soil, but watered with a solution of nitrate 

 of potash, are charged with that salt. 



Generally speaking, a superabundance of salts, 

 especially it' they he of kinds very soluble in wa- 

 ter, injures vegetation; this is particularly ihe case 

 when the salts are not such as enter naturally into 

 the plants, among the number of their constituent 

 principles. Salts of foreign natures cannot be use- 

 ful, excepting as they may serve, in very small 

 quantities, to excite and stimulate the organs of 

 plants. The great value of sulphate of lime as a 

 manure, is owing to its insolubility, which allows 

 water to contain but a very small portion of it at 

 once; so that it passes into plants very gradually, 

 and thus its effects are prolonged for several years; 

 till, asl have before observed, the soil is exhausted 

 of it. 



The quantity and quality of ihe salts contained 

 in plants may be ascertained by an analysis of the 

 ashes arising from burning them in a dry state. It 

 may not be useless to mention here some facts 

 which may throw light on this subject. 



Kirwan and Ruckers have proved, ihat an equal 

 weight of herbaceous plants furnishes more ashes 

 than of ligneous plants. M. Pertuis has found, 

 that the trunks of trees afford less ashes than the 

 branches, and these last less than the leaves. Ever- 

 greens yield less ashes than trees and shrubs that 

 shed their leaves in autumn. On ihe other hand, 

 Hales and Bonnet have observed, that the perspi- 

 ration of herbaceous is greater than that of ligne- 

 ous plants, and that that of evergreens is less than 

 that of plants which shed their foliage. These 

 circumstances may explain why some plants afford 

 more ashes than others. The water which is 

 evaporated by transpiration deposites in the cells of 

 the plant the salts which it had held in solution, 

 and is replaced by a new quantity, which is in its 

 turn thrown out, leaving behind it an additional 

 portion of salts; so that those, planis, and those 

 portions of the same plant, which transpire most, 

 must necessarily contain the greatest quantity of 

 salts. 



The salts and earths contained in plants are of 

 the same nature as those existing in the soil in 

 which ihey grow, but not, according to analysis, 

 in the same proportions; because the plant absorbs 

 more or less of them according to its own nature 

 and their solubility. It cannot, however, be 

 Btrictly said, that all the salts contained in plants 

 existed previously in the soil, as some neutral 

 salts are evidently formed within their organs; 

 euch are those of which the acid is known to us, 

 and particularly those that contain in their compo- 

 sition a vegetable principle: of this sort are the 



acetates, the malates, and the citrates. The salts 

 do not exist after the burning of the plant, because 

 their acid is decomposed by the action of fire, and 

 ihere remains only the base, which is usually pot- 

 ash or lime; but an analysis of the plant "by ihe 

 wet way'''' gives proof of their existence. 



It is even possible in some cases to follow the 

 formation of the acid, by observing the progress of 

 vegetation, and the changes produced in its pro- 

 ducts. Of this I will mention one example, Beets 

 gathered late in autumn, in the north of France, 

 do not yield the same principles as Ihose gathered 

 at the same period in the south of France; the. first 

 contain sugar, the second saltpetre. Accordingto 

 the experiments carefully made by M. Darracq in 

 the department of Landes, the best roots of ihe 

 south yield as much sugar in the month of Au- 

 gust and ihe earlier part of September, as those of 

 the north; this sugar then is replaced by saltpetre, 

 of which the acid is formed during the progress of 

 vegetation. It has been observed, that beets con- 

 taining sugar frequently underwent a change du- 

 ring the winter by which the sugar entirely disap- 

 peared, and was replaced by saltpetre; in this case 

 we can almost follow with the eye the process of 

 decomposition. The juice of beets in which the 

 change has commenced, when thrown into the 

 boilers, becomes covered with a thick, white foam, 

 which gives out a reddish vapor of nitrous gas; in 

 this state the labor of extracting sugar becomes 

 very difficult; the sugar crystalizes badly, and the 

 proportion of molasses is very great. It may be 

 seen clearly, that in this state oxygen is already 

 united in the beets with azote, and that only an 

 additional portion, which would be gained during 

 the progress of change in the roots, is wanting for 

 the formation of nitric acid; this combined with 

 the potash, which is contained in these roots in the 

 proportion of 1.100 of its weight, would produce 

 >a't;.;'tre. 



It' we observe a plant during ihe various stages 

 of its vegetation, we shall perceive at these diffe- 

 rent periods very remarkable difference in ihe odor, 

 taste, consistency, &c; from this circumslance we 

 must suppose that it forms new products, new 

 combinations, and consequently new salts. 



The alkaline salts are the most abundant in 

 green herbaceous plants. JVI. de Saussure has ob- 

 served, ihat the ashes of young plants that grew 

 upon a poor soil, contained at least | oftheir weight 

 of alkaline salts, and that those of leaves of trees 

 which grew from their buds contained at least £. 



The proportion of alkaline salts diminishes in 

 proportion as the plants advance in age ; this re- 

 mark ap.plies equally to annual plants and to the 

 leaves of ihose trees that shed their foliage in au- 

 tumn. The ashes of seeds contain a greater pro- 

 portion of alkaline salts, than those of the plants 

 that produced them. 



These facts are very important to those who are 

 engaged in the manufacture of salts furnished by 

 the combustion of vegetable substances; since they 

 show clearly that it cannot be equally advantage- 

 ous to them to consume all sorts of plants, nor at 

 all periods of their growth. 



Next to the alkaline salts, the earthy phos- 

 phates of lime and magnesia are the most abundant 

 in plants, and like the first, these diminish in quan- 

 tity in proportion to the age of the plant. Plants 

 also contain, but in very small proportions, silica, 

 and some metalic oxides, especially those of iron. 



