16 BULLETIN 802, U. S. DEPARTMENT OF AGRICULTURE. 
siderable thicknesses. The high content of organically combined 
nitrogenous substances is mainly related to the botanical composi- 
tion of the plant remains and their slow disintegration capacity. 
They are largely of protein origin, but partly chitinous, " coprog- 
enous,'* in nature, being skeletal portions and Qgg cases of ins 
and other animal life, and to some extent derived from spores and 
mycelial components. They are extremely resistant to decomposition. 
A high content of nitrogenous peat substances should not be looked 
upon necessarily as an important factor in judging the mammal or 
soil value of peat and muck. Materials from other types of plant 
remains, though exhibiting smaller values of resistant organic nitro- 
gen, offer greater possibilities for meeting the agricultural and other 
requirements for soluble nitrogen. 
Features such as those described above, especially regarding the 
ether and alcohol soluble component, make the material valuable for 
fuel as peat powder or as machine peat in the form of air-dried 
brick-shaped blocks and for coking or distillation products, pro- 
vided the ash content is lovr. They are relatively less desirable 
for agricultural purposes or for use in gas generators on account of 
the presence of the resistant components and pitch-yielding and 
soot-forming by-products. 
Frequently the material shows a mottled coloring on account of the 
presence of sulphur accumulating either in a finely divided form, as 
I] nodules, as crystals of iron and lime compounds, or in organic 
combination. Ferruginous inclusions are likely to be unavailable 
or injurious when available: they generally add some shade of red 
or yellow to the peat material when air dry, or, more rarely, the 
bluish tint of the phosphatic iron compound " vivianite " (blue iron 
earth). Contaminations of that kind in fields not suitably drained 
retard considerably the growth of crops unless the peat material is 
well aerated, underdrained, limed, or supplied with finely ground 
rock phosphate and potash-bearing minerals. As mud baths, the 
saline phases of these types are reported to have proved medicinally 
valuable, and in European countries they have become the centers 
of health resorts. 
MACEBATEB TYPE. 
" ^ludde."' •' Sapropel," " Gyttja." 
Eeddish brown to deep brown, more or less macerated plant re- 
mains with a fine-grained, oozelike plastic to sticky ground mass in 
various proportions, which occurs as a filler or binding material in 
the interstices between the less easily destructible fragments of plant 
tissue. The material is derived indiscriminately from vegetation 
units bordering open water. Some of the original identity and 
form is retained in spores, pollen grains, seeds, leaf}' and other frag- 
