22 
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 sufficiently 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 alg&e 
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 gelatinous, 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 dry. 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 mainly in basins which are fed by 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 
covered 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. Eepresentative 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. 
