86 BOTANICAL GAZETTE [AUGUST 
It was probably a period of winds, cooled from the ice sheet, and 
of loess deposition. The accumulation of drifted, wind-blown 
sand in the Kankakee, Indiana, area, portions of which were later 
covered by peat materials from a basal forest, may be referable to 
the first two glacial substages. In the general shifting of climatic 
belts the cold climate along the border of the retreating ice prob- 
ably passed into dry windy conditions. On the exposed ground- 
till only marsh plants and low shrubs may have been the dominant 
plant population. This period of relative aridity in turn gave 
place to a second great advance of ice, the late Wisconsin, probably 
not of as great severity as the first, after which a prolonged warm 
and somewhat humid climate prevailed. This appears to have 
been the period of invasion and wide dispersal of forest trees from 
the south, and of a more northerly distribution of certain species 
than is now recorded for them. As to the end of the late glacial 
time, the climatic characteristics from the last glacial recessions 
to post glacial and present conditions stand as yet considerably ill 
defined. The evidences indicate periods during which the climatic 
zones shifted again somewhat. There appears to have been a 
return to cooler and drier climatic conditions, followed by a tem- - 
perate and more humid period than exists at the present time in 
the same localities. The present period is probably approaching 
a climate of rising temperatures and (or) decreasing precipitation. 
The botanical data, however, are as yet insufficient to permit more 
definite conclusions, and they are wholly inadequate for drawing 
a parallel between the past climatic conditions of different countries. 
The writer has had considerable hesitation in publishing the 
climatic correlations for the peat deposits of these great morainic 
systems. Although the interpretation accounts for a series of 
facts that are in need of being formulated, yet there might perhaps 
be another way of correlating the field observations. For this, 
however, the work of several years will doubtless be required. 
This preliminary paper may aid in the meantime a field of peat 
investigations to which Biytr (2), WEBER (35), and others have 
been among the first contributors. With these major climatic 
fluctuations as a basis, chronological data of considerable value 
may perhaps be obtained by this method of peat investigations 
