1921] DACHNOWSKI—PEAT DEPOSITS 71 
for types with water poor in saline food constituents, while meso- 
trophic is applied to the peat materials in the intermediate stage 
g. 4). 
Another significant difference lies in the fact that the final 
climatic vegetation unit of a particular region, for example, a de- 
ciduous forest (fig. 12) or a coniferous forest, is also the climax 
stage of the sequence of peat materials in lacustrine deposits. 
Successionally the sphagnum and heath shrub vegetation units 
appear to be a later stage in the structural development of peat 
deposits. Their superposition upon marsh or forest types of plant 
remains, however, is not to be considered an anomaly or an excep- 
tion. The sequence stands in the same causal relation to develop- 
ment as is the case with other vegetation units. Here, however, 
it is connected with the fact that the ground waters of peat deposits 
in this stage of development are deficient in mineral salts, and that 
bog mosses absorb and retain large quantities of rain water on 
account of their anatomical structure. Sphagnum peat materials 
reach their greatest thickness in cool humid locations with abundant 
rainfall, and contain as a rule only little mineral matter. Theo- 
retically the sphagnum stage in the structural development of a 
peat deposit should be succeeded by shrub, and finally by forest 
stages in the course of time. Actually this does not appear to 
take place, unless the layer of moss peat has been reduced in volume 
by disintegrating processes, and as a result becomes more permeable 
to ground waters. In the present state of our knowledge it is 
impossible to be certain that disintegration can occur without a 
change in climate. Thus the “horizon peat” between the lower 
(older) and the relatively more recent (upper) sphagnum peat in 
northern Germany (fig. 4) is regarded by WEBER (36) as due to 
a climatic change unfavorable for the growth of sphagnum mosses. 
Von Post (23) has corroborated this view by his work in Sweden, 
VAN BarEN (1) confirmed it for some of the peat deposits of the 
Netherlands, and ZAILER (37) verified it for the peat deposits of the 
Enns Valley in the Austrian Alps. The layer is assumed to indicate 
a long interruption of peat formation, during which the high moor 
was covered with Eriophorum and Calluna, and sometimes with 
forest. WEBER and von Post conclude that the horizon peat 
