114 ILLINOIS ACADEMY OF SCIENCE 
ridge 20 to 50 feet high has been built up and in some parts 
strengthened by a grassy fore-dune. The ridge is completely 
fixed and was evidently formerly covered by a mesophytic 
forest of maple, beech, and hemlock, with a small amount of 
Abies balsamea, Picca canadensis, and Populus balsamifera at 
the outer edge. This has been cut off, and the dune cover now 
consists of a few remnants of trees and coppice from the former 
forest, together with such pioneers as Betula alba papyrifera, 
Prunus pennsylvanica, Populus grandidentata, Ostrya virgini- 
ana and Acer spicatum. 
A most distinctive shrub association has developed upon the 
gravel of the Nipissing beach as well as upon the low dunes 
which are developed before or are percehd upon it. It occurs 
both upon High and Beaver Islands, and is characterized by 
low growth, small thick leaves, a large amount of vegetative 
propagation from buried stems and by a decided scarcity of 
grasses. On Beaver Island a scanty sprinkling of Agropyron 
dasystachyum is almost the only grass present, but on High 
Island there are in addition small amounts of Ammophila 
arenaria, and Calamovilfa longifolia. The effect of exposure 
to the strong winds of the west and south-west seems to be the 
cause of a decided dwarfing in all the larger shrubs. Species 
that upon other dune habitats attain a height of 3 to 6 feet or 
even more are here reduced to a foot or less. Prunus pumila, 
Cornus stolonifera and Salix spp. afford examples of such 
dwarfing except when they occur within the shelter of the suc- 
ceeding border zone of forest. The same thing is true of Pop- 
ulus balsimifera which is seldom more than a yard high among 
the shrubs, although it occurs rather freely within that associa- 
tion. 
The composition of this association varies somewhat, 
although generally its dominant members are Arctostaphylos 
Uva-ursi, Prunus pumila, Salix longifolia, 8. syrticola, Populus 
balsamifera, and in some localities Potentilla fruticosa and 
Cornus stolonifera. With these broad leaved shrubs Juniperus 
horizontalis and J. communis mingle freely and in places be- 
come dominant with the gradual elimination of the willows, 
cherries, and poplars. Hither the broad or needle leaved 
shrubs may be succeeded by the trees of a marginal shore forest 
