366 BOTANICAL GAZETTE * [NOVEMBER 
able extent are occasionally met with. In the region of the great 
plains they are sometimes found beneath a surface covering of sand 
and wind-blown deposits. Topp (54, p. 121) has mentioned the 
occurrence of such peat deposits in eastern South Dakota. BArsour 
also reports such deposits from central and eastern Nebraska (2). 
On the basis of their field relations and certain fossils which they 
contain, they are believed to be of Glacial and early Pleistocene age. 
If the plant materials of thése deposits could be carefully work 
over with reference to their successive floras, we might hope for some 
new light on glacial climate, since a part of the deposits are beyond 
the margin of the Wisconsin ice sheet. But even their location and 
existence give evidence of climatic change, and plant and animal 
migration. Although now widely separated from the region of 
active bog formation, they are historically connected with this division. 
Among the mountains of both the eastern and western United 
States, bogs and swamps are to be found in association with mountain 
lakes. More frequently than otherwise these depressions ate con- 
nected with former local glaciation, perhaps the most frequent 
situations being those afforded by the damming back of _ by 
terminal and lateral moraines. Basins for peat accumulation ar 
also found in solid rock made by glacial erosion. The conditions 
here are quite similar to those of the north, the altitude bringing 
about the same general effect as the latitude. The analogy is stil 
further shown on mountains in moist regions where alpine meadows 
are strongly developed. Not only are the plants related to those 
of the tundra, but the deposition of peat or humus is again irrespective 
of basins. F 
In many places east of the great plains there is another pee 
situation not directly connected with glaciation, but in which veget4 s 
débris may accumulate to considerable thickness, vizZ-, o 
débouchure of cold springs. Toward the north these springs ee 
bring about humus accumulation on slopes, but further south pe 
is usually associated with pools and small lakes. 
The second group of situations in which peat accumul 
place on a grand scale, are those associated with coastal 
nomena, such as the rising and sinking of the land, 
deposition of alluvial materials in deltas, and the exte 
ation takes 
plain phe- 
e 
nsion of the 
