18 organic matters; vegetable substances. 



ORGANIC MATTERS. 



Fertile soils always contain organic matters. By this term, however, is not intended to 

 be understood a definite compound, but a complex substance derived from the decay of or- 

 ganized bodies, and existing in various states from the recently dead vegetable leaf or stem, 

 to the perfectly disorganized product or products which have been formed in the process 

 of decay. These products become finally converted into organic acids, which are capable 

 of uniting with bases, as potash, soda, lime, magnesia, iron, manganese, ammonia, e'c. In 

 the character of salts, these compounds are absorbed by the roots of vegetables ; and they 

 constitute, at least in part, their food, and minister to their growth. 



Some theoretical chemists look upon tire organic matter of soils as of little consequence. 

 If, however, the subject is considered in all its bearings, I believe its importance will be 

 conceded. There are important functions which organic matter performs in soil. In the 

 first stages of decay, and indeed through all its changes, it is an absorbent of water and 

 ammonia. Indeed, the absorbent power of a soil is in a direct proportion to its organic 

 matter in a minute state of division. In this respect it ranks higher than clay : it preserves 

 the porosity of soil ; it is a source of carbonic acid ; it aids in the decomposition of the 

 peroxide of iron, by which ammonia is furnished. We therefore find it an active agent at 

 all times, performing some of the most essential offices to the growing vegetable ; offices, 

 which, though they may not be regarded as vital, yet unprejudiced minds must admit are 

 of the highest consequence. 



SUBSTANCES PECULIAR TO THE VEGETABLE KINGDOM. 



Starch. This well known substance is a product of many plants, in some of which it is 

 quite abundant : this is the case with the potato, wheat, barley and oats. It consists of 

 rounded grains imbedded in the cellular tissue, and entirely destitute of a crystalline struc- 

 ture. Starcli is insoluble in cold water ; and, hence, after the cells in which it is contained 

 are ruptured, it may be washed freely, and obtained in a pure state. The starch which is 

 deposited in the tuber of the potato, and in grains of the cereals, is changed by germination 

 into sugar : this transformation is effected by the saccharine fermentation. This suscepti- 

 bility of starch being converted into sugar, is turned to advantage by brewers, in the 

 formation of alcoholic liquors. A seed, when it begins to germinate, absorbs water and 

 swells up, and its temperature rises : it then absorbs oxygen, and evolves water and car- 

 bonic acid, and the starch gradually diminishes or changes into sugar. Soon the sugar 

 itself disappears, by ministering to the growth of a sort of stem. The office of the starch 

 in the seed, tuber and root, is to furnish nutriment, until the plant can obtain it by its 

 radicle from the soil. So long, however, as the seed is kept in a dry place, its starch 

 remains unchanged. 



Lignin, Wood of plants. There are various forms of this substance ; thus, the cells of 



