36 BULLETIN 802, TJ. S. DEPARTMENT OE AGRICULTURE. 
in barrier formation or, more likely, with the accumulation of 
plant remains, and it practically maintained itself over the area of 
active peat formation in close adjustment to the growth of the 
plants holding back the natural drainage. Areas of that class of 
peat deposits can be drained to the bottom and rarely need the 
more elaborate drainage measures which aim to reduce the amount 
of overflow in swamps and marshes resulting from river inunda- 
tion. 
Attention needs to be called to the fact that the dominant timber 
component alone is not always significant of the capabilities of these 
types of peat material. The plant remains derived from evergreen 
shrubs, such as the azalea and rhododendron, or from deciduous 
undergrowth in forests may alter the value of the material con- 
siderably. This is well illustrated in the distinction made by some 
authors between the " mild humus " characteristic of deciduous for- 
ests, well aerated and containing beneficial soil organisms, and the 
" raw humus " found in coniferous forests in which decay-producing 
organisms are usually less abundant. 
ALDEE-WILLOW TYPE. 
" Alnus-Salix peat," " Bruchwaldtorf." 
BIECH TYPE. 
" Betula peat," " Ubergangswaldtorf." 
Brown to chocolate-brown peat material, wickerlike in appear- 
ance on account of the numerous small twigs and branches of alder 
(Alnus spp.), willow (Salix spp.), and other species of deciduous 
shrubs which form a considerable portion in the fibrous or frag- 
mental plant remains. The woody components often consist of 
bark and other recognizable, slowly disintegrating i^arts from birch 
(Betula spp.), but with the exception of the resinous components the 
material is as a rule relatively soft, easily cut, and tends to become 
brittle and granular when dry, breaking down into a blackish 
coarsely grained debris. Material which is well disintegrated or 
contains a large proportion of plastic ground mass takes on a com- 
pact structure and often resembles a hard substance when dry. 
The plant remains are derived from shrubs, among which the 
alders, buttonbushes, and willows are the most common. Birch and 
ericaceous heath shrubs appear to be more numerous in individuals 
on peat deposits of the Northern States and in European countries. 
The analyses presented in Tables I and II are intended to point out 
some of the features of practical value to agriculture and to tech- 
nical interests. 
DECIDUOUS-FOREST TYPES. 
" Laubwaldtorf." 
Loose, mingled debris of partly decayed branches, twigs, bark, and 
other aerial parts of plants falling to the ground and becoming in- 
