PRAIRIE OPENINGS IN THE FOREST. 
BY B. SHIMEK. 
Treeless openings in otherwise forested areas have long been known 
to fieldwvorkers in this part of the Mississippi valley. These openings 
are striking because of the absence of trees, but their flora differs also 
from the minor flora of the forest, being in fact the typical flora of 
the drier prairies. It matters not how remote the greater prairie areas 
may be, or how completely these openings may be surrounded by forest, 
their flora is invariably of the same general prairie type. 
They are exceedingly variable in extent. Sometimes they have an 
area of only a few square rods, as is (or was) the case in the more 
heavily timbered parts of the state; again they are mere tongues of the 
general prairie and naturally blend with it, as in the rougher western 
parts of the state. 
They differ in the nature of their soil. In the northeastern part of 
the state they occur on the driftless surfaces whether covered with loess 
or geest; they are equally present on all the types of drift sub-soils 
from the Kansan to the "Wisconsin ; they are well-developed on all kinds 
of loess surfaces; and they are common on sandy and alluvial areas. 
But whatever^ may be the differences between them they agree in 
occurring uniformly on the rougher surfaces of the state, and they have 
the same flora. 
The naturally timbered areas of the state are rough, and the prairie 
openings are more or less distinctly contrasted with the forest. Some- 
times, especially where there are abrupt changes in topography, the 
line between the prairie openings and the forest is sharp ; again the two 
types blend and a scant sprinkling of trees, usually stunted hard- wood 
species such as oaks, etc., encroaches upon the prairie border producing 
the typical ‘‘oak-openings” or “oak-barrens,” Their distribution sug- 
gests that this rough topography accounts for their existence, for they 
occur uniformly on surfaces which are exposed to the two great factors 
which determine evaporation — namely, the sun and wind. They are 
therefore usually located on the very tops of the ridges, or on the south- 
