1847.] The Organic Matter of Soil. ' 95 



of which is to supply ammonia or rather nitrogen to the growing 

 plants. Air and water, then, contain the elements which make 

 it possible for the organic matter of the soil to return once more 

 to that vital state in which it exists in living vegetables, or in 

 other words, to become the food of plants. 



If we now trace the changes which decaying wood undergoes, 

 from the time when it first ceases to be a living body to that last 

 change by which it is fitted for the function of nutrition, we shall 

 be able to see its use in this part of the economy of nature. Wood, 

 when it has lost its vitality, goes to decay, but the progressive 

 changes which it passes through are not analagous to putrefaction. 

 Rotten wood, as it exists in decayed trees, is a neutral substance; 

 neither acid nor alkaline at first. But in progress of time, seve- 

 ral definite substances are formed from it, which possess activity 

 and belong mainly to the class of acids, and are capable of com- 

 bining with the alkalies and alkaline earths which are soluble 

 salts, and in this state minister to the growth of plants. Of the 

 substances which are formed by decaying wood, and by peat or 

 muck, ulmine is one, which is also a neutral body, and is quite in- 

 soluble, and hence is not useful as a nutriment. This substance 

 is called uhnine from the fact that it was first prepared trom the 

 wood of the elm; but it is found in all other kinds of vegetable 

 matters which are undergoing the changes already alluded to. 

 Ulmine is formed from wood, or fibrous, vegetable matter of any 

 kind, as leaves, twigs, &c., b}- the absorption of oxygen from the 

 air, or contained in the moist earth. By a simultaneous action 

 carbonic acid is liberated. The substance formed may be repre- 

 sented by C33, H27, 0^4 ; 33 equivalents of carbon, 27 of hydro- 

 gen, and 24 of oxygen. The substance represented by this for- 

 mula is a white, friable substance, found in the interior of hollow, 

 decaying trees, and is produced by the oxidation of the woody 

 fibre. Lignine also produces other bodies by combining with 

 oxygen. Thus, 4 atoms of lignine,* €43, H32, O32, with 14 of 

 oxygen, produce 8C. Oo with 18H. 0.; and an atom of ulmine, 

 C40, Hi4, 0]2. Other products of an analogous kind are formed 

 from wood by union with oxygen. Of these, humus and humic 

 acids are among the most remarkable. The first is represented 

 by the formula C40, H14, Oio; the latter by C40, H15, O15. These 

 two acids, which are spontaneously formed, and are common in 

 peat and other earths, differ from each other in their relations to 

 ammonia; the first having no aflBnity for it, while in the latter it 

 is so strong that it is difficult to separate them. In consequence 

 of this affinity, it no doubt forms an important element in pro- 

 ductive soils. 



Kane's Chemistry, edited by Draper, p. 638. 



