86 SOILS: PBOPJERTIES AND MANAGEMENT 



ing organic matter. Year after year this process goes 

 on, and year after year the bed of cumulose material 

 becomes deeper and deeper. Large shrubs, and even 

 forests, often grow on such land. Time and the lack of 

 water are the factors that may limit the depth of such 

 beds. Accumulations of this nature are found dotted 

 over the entire country. Their size may vary from a 

 few acres to several thousand. Along streams the old 

 abandoned beds offer a common opportunity for the 

 beginning of such accumulations. Along large bodies 

 of water, marshes, either salt or fresh, may allow the 

 process to go on. Shallow basins scraped and gouged 

 out by advancing glaciers are frequently occupied by 

 such material. In the last-named case the beds are 

 more or less independent of topography, and may be 

 found on hillsides^ or even on hilltops, as well as in the 

 lower lands. 



Cumulose materials may be grouped under two heads, 

 peat and muck. The only difference is in their stage of 

 decay. In peat the stem and leaf structure of the original 

 plants can still be detected, and identification is quite 

 possible. In muck, however, the putrefaction and decay 

 have gone so far that the plant tissue has lost its 

 identity as such and is merged into that complicated 

 and indefinite material called humus. The composition 

 of peat and muck may be much altered by the wash- 

 ing-in of mineral matter from above. In some cases 

 the beds may be from 80 to 85 per cent organic, while 

 in other cases, due to this foreign material the percent- 

 age may drop to as low as 15, giving a black or swamp 

 marsh mud. 



The following analyses illustrate the composition of 

 representative cumulose soils: — 



