I 
IOWA ACADEMY OF SCIENCES. 109 
that the species of plants whose remains occur in these 
widely separated deposits afford some definite and trust- 
worthy information regarding the climatic conditions that 
prevailed during the Aftonian interval. 
Buried forests beds and fragments of the wood of trees 
which now flourish in more northern latitudes have been 
found at various points in Iowa. Where these trunks 
and wood fragments occur on the surface of a soil horizon 
they may represent only such trees as were growing at the 
close of an interglacial interval, and were overwhelmed by 
the oncoming of the ice. These forests may be such as 
were developed near the close of the interval in response 
to a climate that was cooled by the proximity of the 
slowly advancing glacier. 
If the bed of vegetable material in Union county, and 
that at Oelwein, represent a long continued accumulation 
which took place neither at the very beginning nor at the 
very close of the Aftonian age, the species of plants 
whose remains are found in these deposits would testify 
to the general character of the Aftonian climate, unmodi- 
fied by cooling winds that blew either from advancing or 
retreating ice masses. 
The scarcity in these deposits, of fragments of our 
deciduous forest trees, and the presence, in abundance, of 
leaves and twigs and pieces of wood of cone bearing trees, 
such as live at present in higher latitudes, is significant. 
The absence in these beds of the aquatic moss species 
that predominate today in the lakes and pools of Iowa, 
and the occurrence there of species of mosses which now 
flourish further northward, furnish strong evidence that 
during the Aftonian age the climate of our state was 
favorable for the growth of a more boreal vegetation 
than at present. 
The conclusion seems warranted that many of the plants 
which are found in the present flora of our state had no 
place here during that earliest interglacial interval, and 
that, at our latitude, the climate never became so mild and 
genial throughout this period as that which the region 
enjoys during the present age. 
