MICHIGAN ACADEMY OF SCIENCE. 
63 
iii exceptional eases that they were formed as normal dunes, namely, by 
the collecting of sand around a nucleus. They were usually the result 
of a heaping up of the sand by the pushing of the ice of the lake. 
Generally the aspen association takes possession of these ridges. A 
somewhat different composition of species, however, always obtained. 
Pop ulus tremuloides is accompanied by less xerophytic trees such as 
red maple, white birch, while cedar, Populus Jmlsamifera , red oak and 
Norway and white pines. Associated with the trees there may be 
shrubby plants as poison ivy, rose ( Rosa Manila), bearberry, blueberries 
(Yaccinium pennsyl m nicuni and V. canadense), red-osier dogwood, wil- 
lows, together with herbaceous plants as wild rye, Spartina michauxiana , 
Aster laevis , etc. 
Other stations on the fringing dune were occupied almost exclusively 
by a stand of willows, three to five or six feet high, with a few of the 
normal secondary species of that association. 
In stations along South Fishtail bay and in a few stations along 
the southwestern shore of Douglas Lake, this ridge appeared more like 
a real dune. It was covered by. a dense growth of Elymus canadensis 
in which might be mixt Spartina michauxiana, and less frequently a few 
secondary species as Apocynum cannabinum, bearberry and blueberry 
( Yaccinium pennsylvanicmm) . Such a dune is shown in Plate 9. 
There were no plant associations leading up to this dune association. 
It is an example of poineer occupation of a newly formed physiographic 
habitat. The presence of bearberry indicates that normal succession 
tends towards the development of a heath but the heath is so feebly 
represented in this region that before such a stage can obtain existence, 
other associations replace it. Of these the willow ( Ealix-Cornus Associa- 
tion), and the aspens are most frequent. In other places pines and 
even hardwoods may succeed the Elymus association. In cases where the 
ice merely pushes up over the shore into the surrounding vegetation, 
in the absence of any dune-like formation, Elymus was not found. The 
upland association ended abruptly at the limit of ice work. 
The Heath Association. 
A few patches of bearberry, Arctostaphylos uva-ursi, growing under 
the pines that fringe South Fishtail bay is all that remains to indi- 
cate the former presence of the heath association in this region. These 
plants seen to be persisting, but rarely show any evidence of spreading- 
out into genetically lower associations. With the bearberry was asso- 
ciated the blueberry (Yaccinium pennsylvanicum) . 
The Pinus banlcsiana Association. 
This association of conifers, which develops on the poorest land 
adaptable for tree growth, was not formerly present in the region, altho 
scattering trees of Finns banlcsiana occurred here and there. With the 
extreme and thuro burning that has occurred on the land formerly occu- 
pied by Pinus strolnis the soil has been very much depleted. In the area 
between Douglas Lake and Pellston, aspens have followed lumbering 
and thuro burning, but the aspens have made but little headway. Seed- 
lings of Pinus banlcsiana are coming in here and there among the aspens. 
