JAISUAKY, 1902. BRUXCKEN STUDIES IN PLANT DISTRIBUTION. 
17 
Studies in Plant Distribution. 
By ERNEST BRUNCKEN. 
J. On the Succession of Forest Types in the Vicinity of Milwaukee. 
In a former paper (Bull. Wis. Nat. History Society, I, page 
178) the forest conditions in the vicinity of Milwaukee were con- 
sidered principally from the economic standpoint. The following 
pages are an attempt to treat some of the peculiarities of the for- 
ests of the same region from the standpoint of ecological distri- 
bution. 
The forests of the Milwaukee region are almost exclusively 
of the deciduous, mesophytic type, xerophilous associations being 
now represented only by the meager remnants of tamarack 
swamps still lingering here and there. But there is evidence of 
the former prevalence of xerophytic, principally coniferous asso- 
ciations ; and within the mesophytic association a number of dis- 
tinct groups of more or less pronounced mesophily can be clearly 
distinguished. Between these sub-associations a vigorous con- 
test is carried on, so that there are numerous transition stages. 
The mesophytic association may be conveniently divided into 
three sub-associations, according to the degree of mesophily ex- 
hibited in the species of which they are most prevalently com- 
posed. These sub-associations are: 
1. The hemi-xerophytic sub-association. Its characteristic 
species are various oaks, particularly the white and burr oaks ; the 
shell-bark hickory and the black cherry. 
2. The mesophytic sub-association, with the basswood, the 
hard maple, and in a part of the region the beech ( i ) as its most 
characteristic members. 
3. The hemi-hydrophytic sub-association, in which various 
elms, black ash and cotton wood are leading species. 
The first of these sub-associations is probably the most widely 
spread in the region. It is characterized by the great light de- 
mand of the trees composing it. In addition to the species men- 
tioned, we find in this sub-association Quercus rubra and tincto- 
ria, Ostrya Virginica, Populus tremuloides and grandidentata 
Hicoria ovata and glabra. The underbrush shows, in addition 
to^ the young seedlings and saplings of the trees, several shrubi 
with xerophytic characters, such as various species of Ribes, haz- 
(1) On the peculiarities of distribution of the beech, see Wis. N. H. S. Bulletin, I, 
page 33. 
