102. 



or secretions which are able to dissolve other substances. Fungi dis- 

 solve rock and wood alike. There is a continual proces.:. of chemicr 1 

 disorganization and of recoraposi tion to other forms, and to new forms. 



These processes are now going on as in the pant and they will go 

 on indefinitely. Leaching is a good example. 



. Soil transportation. Many soils are not in place, especially 

 in gla.cir.ted ru/jioris; a great pnrt of the surface of the earth is over- 

 laid with alluvial or wnter soils; wind-carried soils nnd loess cover 

 over 1/6 of the land area, which rep.lly is an immense area* 



All riv.-ra and other run-off s carry away materials and soils 

 "bodily, and deposit them as sorted materials, classified to coarse, fine, 

 and he-'v/y soils, and characterized by deposition of like soils. Ground 

 water constantly carry away a part of the soil; the amounts are usually 

 small individually, but the aggregate is large. Leaching plays an irapor- 

 tnt pn.rt here. This action is faster in a wet country than in a dry 

 one. Both surface and underground run-off s or transportations are in- 

 fluenced by the character of the soils thru which they pass, and by 

 absorption anci solution. 



<i. Humus formation. The formation of humus is due to the actions 

 of livirT ni si-is, especially "bacteria which decompose organic ma- 

 terial. The chief product of this action is CG2. H^COj or carbonic acid 

 is used .iure of decomposition. This process is influenced by 



the influences of bacteria life. Any injury to bacteria injures humus 

 formation, vhich depends on. 



temperature 



moisture 



freedom from poisonous materials (iron salts) 



mineral iwi 



Kuinus formation takes place ten times as fast at 80 summer than 

 at 50. Cry soil stops the formation of humus. 4J of water content gave 

 an action which 1? primes as fast as was obtained from 7% with humus $Jfctt 

 (compos). Oxidation is an important factor in forming humus. If humus 

 be left in a pile for a sufficient length of time it will change to 

 port, then to lignite, and to anthracite. 



Nutritive salts necessary: bacteria need K, JNaO, etc., for growti 

 Plenty of lime allows an easier formation of humus. Oxygen gives aera- 

 tion, which is very favorable to the process. 



A distinction should be made between decomposition and ferraen- 

 tion: the former often includes the latter: fermentation produces a 

 change to: 



1) marsh gas 



21 to ? 



3) to hydrogen, 



The change of leaves to humus is interesting. The steps of this 

 process are substantially as follows: 



Leaching out of salts. 



Leave* are more or less broken, by animals, etc. 



Decomposition by filamentous fungi. 



4) Further decomposition to humus by bacteria. 



