22 BULLETIN 802, U. S. DEPAETIMEXT OF AGRICULTURE. 



from variations in amounts of well-disintegrated herbaceous aquatic- 

 plant debris; brownish, loose, and mellow when permeated with 

 fibrous roots from grasses, sedges, rushes, and other plants. 



These structural and color characteristics are suiEcientlj- well 

 marked in some deposits to constitute three phases in this subtype. It 

 usually forms a well-marked layer at the greater depth of certain basin 

 deposits, but it has been found also as a surface soil material, notably 

 in a number of river valleys in the New England States. 



The plant remains are derived from diatoms and other vegetation 

 of microscopic size and simple structure, such as desmids ; green algse 

 and species of Utricularia, Lemna, Eiccia, and others are members of 

 the vegetation unit floating freely in the quiet water of ponds and 

 rivers. 



Agricultural practices and possibilities are relatively unknown. 

 Species of Calamagrostis, Phalaris, and Carex form the domi- 

 nant vegetation cover of siliceous deposits on meadows of which the 

 subsurface soil consists of macerated peat materials. 



Diatomaceous material has valuable abrasive properties. As " in- 

 fusorial earth" it is often employed for filtering, insulating, non- 

 conducting, or packing purposes, as an absorbent, and for making 

 protective soundproof envelopes. 



COLLOIDAL TYPE. 



" Lebermudde," " Saprokol," " Dy." 



Finely divided, distinctly g-ela'tinous, plastic organic debris, olive 

 green, yellowish brown, or greenish brown in color; dark gray to 

 blackish brown, hard, and of the consistency of horn when dr}^ The 

 material is in large part probably a flocculation product rather than 

 the result of chemical reaction or other transformation, since it has been 

 found mainlv in basins which are fed bv ground waters containing 

 lime in solution or which overlie a calcareous mineral substratum. 

 There appears to be nothing in this type of peat that may be inter- 

 preted as of algal origin. The very small particles of plant remains 

 are chiefly fragments from an aquatic vegetation which probably 

 coA'erecl the open water area to the exclusion of other plant life. The 

 organic debris seems to be derived largely from light-colored paren- 

 chymatous rather than lignitic tissue or waxy and resinous compo- 

 nents. Algal filaments are present occasionally, but less abundant 

 than spores, pollen, seeds of water plants, animal ejecta, and other 

 derivatives. Representative data of a chemical nature are given in 

 Table I. 



The layer is a transitional one, since in position it occurs more 

 commonly between a lower silty or clayey calcareous mudlike debris 

 and an upper macerated type of peat. 



