JULY, 1902. BRUNCKEN — STUDIES IN PLANT DISTRIBUTION. 137 
Studies in Plant Distribution. 
By ERNEST BRUNCKLEN. 
3. Upland Brushwoods of the Milwaukee Region. 
There are in the vicinity of Milwaukee numerous areas of 
greater or less extent which are covered with shrubs, either com- 
pletely, so as to shade the ground and form what are substantially 
forest conditions ; or in more or less sparsely scattered groups and 
individuals, with grass or herb-covered spaces between. The for- 
mer type may be called thickets ; the other heaths. As to thickets, 
the present inquiry will be confined principally to those occurring 
on dry uplands. The extensive thickets found in swamps and 
river bottoms have essentially different ecological relations, of 
great complexity, and will be considered only incidentally. As to 
heaths, the name implies their xerophytic nature. Similar areas 
of groups of shrubs in marshy land are frequent at some little 
distance from Milwaukee, but in the territory under discussion 
are of every limited extent. 
There is no evidence at hand whether before settlement of the 
region upland brushwoods of either class occurred therein. Re- 
garding similar bottom brushwoods the fact is of value that many 
of the very old trees still standing in the river bottoms have low 
branches, as if they had stood free at least from the height usually 
reached by the hydrophytic shrubs. Sometimes these low branches 
are developed on one side only, as if in its youth the tree had stood 
on the edge of a shrub-covered glade. ( i ) 
If the absence of evidence to the contrary makes it probable 
that such glades were not found on the uplands, the shrubs which 
now compose the brushwoods must either have come to the region 
since the settlement, or have existed theretofore in the form of 
underbrush. The latter alternative is indicated by the great fre- 
quency of individuals, the considerable variety of species, and 
above all the fact that the same species to this day occur very 
commonly as underbrush, especially in the hemi-xerophytic for- 
ests. It is not every shrub, however, which occurs in the forest, 
that takes part in forming brushwoods. On the whole, it may be 
said that the thicket-forming shrubs are three in number: the 
witch hazel ; the staghorn sumach, and the various species of haw- 
thorn. A large number of other shrubs are liable to be found 
1. Of course this evidence is not complete. The plades may have been sedpe 
marshes: only, if that was the case, one ought to occasionally find t5ranches still 
lower than the height of 8 to 12 feet at which they mostly occur. 
