10 Rhodora [APRIL 
CLIMATE AT THE CLOSE OF THE GLACIAL PERIOD. 
It may well be questioned whether or not the conditions of life which 
obtained at the close of the glacial period were suitable for the migra- 
gration of coastal plain plants. This question cannot be answered 
very specifically, for no one knows exactly what were the conditions 
of life at this time. But I shall give such evidence as there is. 
As to climate: it might at first thought appear that it would have 
been too cold for coastal plain plants. But it has amply been shown 
upon the best authorities that coastal plain plants have a tendency 
to range up and down the coastal plain from Florida to Nova Scotia 
and Newfoundland without very great regard to the variabilities of 
the several climates of this territory, but with regard chiefly to the 
acid character of the sands and peats which there abound. It is 
probable, therefore, that even were the climate of the Algonquin stage 
fairly rigorous, there might still be an abundance of such types grow- 
ing along the glacial lakes. 
But it is, perhaps, not necessary, to imagine a polar frigidity for 
this stage. The amount of insolation required to melt back the glacier 
must have been very great and as the earth and its vegetation have 
a high coefficient of heat absorption, they received at that time a 
significant amount of warmth!. 
That it was warm enough for plant life between the glacial advances 
is proven by the fact of peat deposits found between glacial deposits". 
This furnishes proof that whatever the climate and the length of the 
interglacial periods, there were not only abundant time but appropri- 
ate conditions for a plant growth suffieient to make considerable 
peat deposits. 
But the glacier might reasonably be expected to make the waters of 
its marginal lakes cold. Even if this were so, it is still true that the 
coastwise lagoons and bays would be shallow and protected, and hence 
would soon heat up. It is in these, or on their margins, assuredly, and 
not in the open waters of the big lakes, that the coastal plain flora must 
have migrated. Terrestrial types would not have been much affect- 
ed by the temperatures of the adjacent waters. 
1 The whole matter of climate at this time has been treated by Dachnowski, Peat 
Deposits and Their Evidence of Climatic Change, Bot. Gaz. Ixxii., summarized on 
pages 85-86 (1921). 
? Chicago Folio of the U. S. Geol. Surv. 11. 
(T'o be continued.) 
