120 NORTH-CAROLINA GEOLOGICAL SURVEY. 



a different kind. In this the elements are chemically combined, and hence 

 they are not so readily .separated from each other, and hence, too, its action 

 is constant, and that which is proper to it in its state of integrity it is the 

 solvent power so necessary to bring all particles to a state of fineness that 

 they may pass into the organism of vegetables ; for solution is merely that 

 separation of particles to that degree of minuteness that they are capable 

 of being suspended in the medium. They are merely farther apart, and 

 they are brought thereby into a condition to undergo farther and more 

 thorough changes than they were previous to their solution or suspension 

 in the medium itself. But certain bodies can and do decompose it, the final 

 end or cause 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 or alkaline at first. But in progress of 

 time, several definite substances are formed from it, which possess activity 

 and belong mainly to the class of acids, and are capable of combining 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 insoluble, and hence is not useful as a nutriment. This 

 substance is called ulmine from the fact that it was first prepared from 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., 

 by 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 represented by C 33 , H 27 , 0^; 33 equivalents of carbon, 27 of hydro- 

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

 duces other bodies by combining with oxygen. Thus, 4 atoms of lignine,* 

 048, H 32 , 32 , with 14 of oxygen, produce 80. 2 with 18H. 0. ; and an atom 

 of ulmine, C 40 , H ]4 , Oi 2 . Other products of an analogous kind are formed 

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



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



