IMPORTANT TYPES OF PEAT MATERIAL. 17 
ments of pondweed material, bits of smooth and pustulate rootlets, 
and in the coarser woody, cuticular, or other resistant components. 
Animal derivatives, such as chitinized skeletal portions and egg 
cases from insects, are frequent. 
The data in Table I are intended to show the marked differences 
which may result from the presence of ether and alcohol soluble 
substances, nitrogenous compounds, and products valued in the dis- 
tillation of peat. 
Seasonal admixtures of clay, silt, and sand produce, as a rule, 
thinly laminated gritty layers, with cleavage planes which often 
contain leafy impressions, small stems, and other drifted material. 
The variations in mineral matter constitute phases of the type when 
the relative proportion, e. g., of iron, sand, silt, or clay, is above 40 
per cent. 
132927°— 19— Bull. 802 3 
