SOIL ORGANISMS 251 



Moor Peat.— Feat mosses (Sphagnum spp.) are especially responsi- 

 ble for the formation of this type of soil. Sphagnum peat, loose, of 

 gray-brown, yellowish, or dark-brown color, contains 96 to 99 per cent 

 of organic matter. Vaginatum peat, formed by Eriophorum vagina- 

 turn, is compact, of fibrous structure, and shiny brown. According 

 to Zaidler, it contains about 98 per cent of organic matter. 



The different kinds of peat have been described and investigated in 

 detail by Waren (1924). He distinguishes three main groups: (a) 

 vascular peat, (6) moss peat, and (c) Hchen peat. 



The vascular peat includes the following varieties: (1) reed peat, 

 (2) Equisetum peat, (3) sedge peat formed mostly from species of 

 Carex, (4) Scheuchzeria peat, (5) cotton-grass peat from Eriophorum 

 vaginatum, (6) twig peat, and (7) wood or forest peat. 



The lichen peat is poorly developed. Waren has also investigated 

 the relations existing between the chemical composition of peat and 

 the vegetation of the bogs and has found that here calcium is of great 

 importance. 



Raw Humus. — The widely distributed raw humus, shunned by 

 foresters and alpine farmers, is a humus layer permeated with fungus 

 hyphae and mycelia and thickly traversed by a network of roots of 

 seed plants, especially of dwarf shrubs. It is sharply marked off from 

 the underlying mineral loam and is in process of decay. Organic 

 components predominate with mineral matter sparsely intermingled. 

 Raw humus always gives a strongly acid reaction. The upper, shghtly 

 decomposed raw humus layer, which still permits at least a partial 

 recognition of the individual plant fragments, is also called dry peat 

 (leaf mold). Large quantities of dry peat are formed only when the 

 forces of decomposition fail to keep up with the supply of dead leaves. 

 In central Europe, therefore, the formation of dry peat does not occur 

 in grassy places, and in southern Europe there is no formation of dry 

 peat. Varieties of this dry peat may be designated Loiseleuria peat, 

 Vaccinium peat, or fir peat, according to the principal plant providing 

 the litter. It must not be confused with undecomposed litter. The 

 formation of raw humus is a result of humid or perhumid climatic 

 conditions with low temperatures. 



Alpine Humus. — Ramann, Leiningen, and others call alpine humus 

 the mild, adsorptively saturated humus of alpine and especially of 

 subalpine calcareous soils. But Braun-Blanquet and Jenny would 

 limit this term to the acid humus, which is to be considered the climax 

 soil of the alpine zone of the Alps, of the summits of the high Cevennes 

 and probably of other mountains with similar climatic conditions. It 

 differs from the alpine humus of Ramann by its high dispersion and 



