1913] COOPER—ISLE ROYALE 193 
the present lake level. It may be that the basin has been more 
recently shut off from Lake Superior than that on Raspberry 
Island, and also the depression is larger and doubtless deeper. 
The climax forest descends to the edge of the interior lake, except 
for an occasional short strip of stony or sandy beach. At the 
southwest end there is a considerable amount of bog vegetation, 
growing in water a few centimeters deep and underlain by 2 m. of 
soft mud containing much organic material. The principal aquatic 
is Nymphaea advena Ait. (yellow pond lily). There is next a zone 
of amphibious plants dominated by Menyanthes trifoliata L. 
(buckbean), which is accompanied by Lysimachia thyrsiflora L. 
(bog loosestrife) and a few other species. As will be noted later, 
Menyanthes is frequently an important mat-former. Through the 
middle of this zone winds a narrow streamlike ribbon of water, 
probably the last remnant of a sluggish outlet. Back of the 
Menyanthes zone and filling the continuation of the basin for o. 5 km. 
is the bog forest, composed of Larix and Picea mariana, with 
Alnus incana (L.) Moench (hoary alder) in front. 
The arrangement of the vegetation here illustrates a feature 
characteristic of the bog-filled depressions of Isle Royale. On 
account of the elongated form of the basins, the building out of the 
bog vegetation goes on much more rapidly at the ends of the lakes 
than along their sides, because of gentler slope. Theoretically, also, 
it should build out faster on the northwest side than on the southeast, 
since by reason of the rock structure the former slope is normally 
gentler than the latter. In a few cases notable difference was seen 
in the width of the sedge mat corresponding to the difference in 
slope, but usually the width of the zone on the two sides was about 
the same. Probably talus deposits, slope wash, and sediments of 
various kinds tend to lessen the slope of the southeast side, making 
it more or less equal to that of the other. 
It has been stated that along the greater part of the lake shore 
the climax forest descends to the water’s edge. At one point (a 
sandy stretch) bog vegetation was found to be obtaining its first 
foothold. Farthest out were scattering plants of Nymphaea advena. 
Close to shore grew scattered stools of Carex filiformis L. (bog 
sedge) and plants of Eleocharis palustris (L.) R. & S. (creeping 
