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BULLETIN- OF WISCONSIN NATURAL HISTORY SOCIETY. VOL. 2. NO. 1. 
basswood and beeches so much better developed in the neighborhood 
of Lake Michigan than they are twenty or thirty miles inland? 
The hypothetical answer which suggests itself is that the nearness 
of so large a body of water has a modifying influence on the hy- 
gricity and temperature relations of the climate, by which the ac- 
cumulation of humus in the oak forests is favored by retarding of 
oxydization. The correctness of this hypothesis can be determined 
by nothing except numerous and long-continued meteorological 
observations in various localities. Such data are not in existence, 
and there is no prospect that the gathering of them will be com- 
menced in the near future. 
The culmination type of forest has not been reached in this 
vicinity anywhere except in small, isolated, specially favored 
areas. By far the greater part of the territory is in a transition 
stage, presenting neither the purely mesophytic nor the hemi-xero- 
phytic character. On the whole it is probably easier to find areas 
decidedly of the latter kind than of the former. It is apparent, 
then, that the course of development from the oak forest through 
the various transition stages to the basswood-maple-beech, or per- 
haps eventually to the pure maple forest, has not yet become 
completed. 
Perhaps it would be more correct to say : Had not been com- 
pleted when the settlement of the region brought in a new factor 
of the greatest modifying power. Not only was the greater part 
of the territory wholly deprived of its forest cover by human 
hands, but the remaining tracts of forest were cut up into small 
parcels, of sizes ranging up to about a hundred acres, but usually 
much smaller. This reduction alone would probably be suffi- 
cient, by allowing the better access of wind to the forest floor, to 
make the conditions more xerophytic, especially as the edges of 
the tracts are rarely protected against the drying influence of the 
wind by a mantle of shrubs. But in addition a great many trees 
have been culled from the forest everywhere, so that frequently 
the crown cover is very much broken and the sunshine has full 
access. This of course increases the rate of oxydization of the 
humus and prevents its accumulation to a great degree. The 
floor in such places is often covered with a dense growth of 
grasses. All these factors tend to reverse the natural progress 
towards the purely mesophytic sub-association. It is quite notice- 
able that taking the region as a whole the oaks are on the increase. 
In many places, especially where there is much grass, oaks are 
practically the only young trees to be found. 
However, there are isolated tracts here and there, on which, 
through accident probably more often than design, the maple has 
