CONSTITUENTS OF PLANTS. 



37 



and also into beer. The bran of flour con- 

 tains the greatest quantity of it. It is this 

 salt which forms large crystalline concre- 

 tions, often amounting to several pounds in 

 weight, in the ccecwn of horses belonging 

 to millers; and when ammonia is mixed 

 with beer, the same salt separates as a white 

 precipitate. 



Most plants, perhaps all of them, contain 

 organic acids of very different composition 

 and properties, all of which are in combi- 

 nation with bases, such as potash, soda, 

 lime, or magnesia. These bases evidently 

 regulate the formation of the acids, for the 

 diminution of the one is followed by a de- 

 crease of the other: thus in the grape, for 

 example, the quantity of potash contained 

 in its juice is less when it is ripe than when 

 unripe ; and the acids, under the same 

 circumstances, are found to vary in a 

 similar manner. Such constituents exist in 

 small quantity in those parts of a plant in 

 which the process of assimilation is most 

 active, as in the mass of woody fibre; and 

 their quantity is greater in those organs 

 whose office it is to prepare substances con- 

 veyed to them for assimilation by other 

 parts. The leaves contain more inorganic 

 matters than the branches, and the branches 

 more than the stem. The potato plant con- 

 tains more potash before blossoming than 

 after it. 



The acids found in the different families 

 of plants are of various kinds ; it cannot be 

 supposed that their presence and peculiari- 

 ties are the result of accident. The fumaric 

 and oxalic acids in the liverwort, the kinovic 

 acid in the China nova, the rocellic acid in 

 the Rocella linctoria, the tartaric acid in 

 grapes, and the numerous other organic 

 acids, must serve some end in vegetable life. 

 But if these acids constantly exist in vege- 

 tables, and are necessary to their life, which 

 is incontestable, it is equally certain that 

 some alkaline base is also indispensable, in 

 order to enter into combination with the 

 acids which are always found in the state of 

 salts. All plants yield by incineration ashes 

 containing carbonic acid; all therefore must 

 contain salts of an organic acid.* 



Now, as we know the capacity of satura- 

 tion of organic acids to be unchanging, it 

 follows that the quantity of the bases united 

 with them cannot vary, and for this reason 

 the latter substances ought to be considered 

 with the strictest attention both by the agri- 

 culturist and physiologist. 



We have no reason to believe that a plant 

 in a condition of free and unimpeded growth 

 produces more of its peculiar acids than it 

 requires for its own existence ; hence, a 

 plant, on whatever soil it grows, must con- 

 tain an invariable quantity of alkaline bases. 

 Culture alone will be able to cause a devia- 

 tion. 



* Snlts of organic acids yield carbonates on in- 

 cineration, if they contain either alkaline or earthy 

 bases. 



In order to understand this subject clearly, 

 it will be necessary to bear in mind that any 

 one of the alkaline bases may be substituted 

 for another, the action of all being the same. 

 Our conclusion is therefore by no means en- 

 dangered by the existence of a particular 

 alkali in one plant, which may be absent in 

 others of the same species. If this inference 

 be correct, the absent alkali or earth must be 

 supplied by one similar in its mode of ac- 

 tion, or in other words, by an equivalent of 

 another base. The number of equivalents 

 of these various bases which may be com- 

 bined with a certain portion of acid must 

 necessarily be the same, and therefore the 

 amount of oxygen contained in them must 

 remain unchanged under all circumstances 

 and on whatever soil they grow. 



Of course, this argument lefers only to 

 those alkaline bases which in the form of 

 organic salts form constituents of the plants. 

 Now, these salts are preserved in the ashes 

 of plants as carbonates, the quantity of 

 which can be easily ascertained. 



It has been distinctly shown, by the analy 

 sis of De Saussure and Berthier, that the 

 nature of a soil exercises a decided influence 

 on the quantity of the different metallic ox- 

 ides contained in the plants which grow on 

 it ; that magnesia, for example, was con- 

 tained in the ashes of a pine-tree grown at 

 Mont Breven, whilst it was absent from the 

 ashes of a tree of the same species from 

 Mont La Salle, and that even the proportion 

 of lime and potash was very different. 



Hence it has been concluded, (errone- 

 ously, I believe,) that the presence of bases 

 exercises no particular influence upon the 

 growth of plants : but even were this view 

 correct, it must be considered as a most re- 

 markable accident that these same analyses 

 furnish proof for the very opposite opinion. 

 For although the composition of the ashes 

 of these pine-trees were so very different, 

 they contained, according to the analyses of 

 De Saussure, an equal number of equiva- 

 lents of metallic oxides ; or, what is the same 

 thing, the quantity of oxygen contained in 

 all the bases was in both cases the same. 



100 parts of the ashes of the pine-tree 

 from Mont Breven contained 



Carbonate of Potash 



Lime 



" Magnesia 



3-60 



46-34 



6-77 



Sum of the carbonates 56'71 



Quantity of oxygen in the Potash - 41 



Lime 733 



" " Magnesia 1-27 



Sum of the oxygen in the bases 9*01 



100 parts of the ashes of the pine from 

 Mont La Salle contained* 



* According to the experiments of Saussure, 

 1000 parts of the wood of the pine from Mont 

 Brevon gave 11 '87 parts of ashes ; the same quan- 

 tity of wood from Mont La Salle yielded 11*28 

 parts. From this we might conclude that the two 

 pines, although brought up in different soils, yet 

 contained the same quantity of 'inorganic elements* 



