1913] COOPER—ISLE ROYALE 137 
Gull Islands.—These are a line of rocky knobs rising 1.5—12 m. 
above the surface of the water. They are projecting points of the 
Greenstone Ridge which disappears under the water at the north- 
east end of Isle Royale, reappears in Passage Island, and again here. 
They are steep-sided in the main, and at one point on the north- 
west side of the largest islet there is a small shingle beach. As the 
name indicates, the islands are favorite haunts of the herring gulls, 
which congregate and breed here in enormous numbers. They are 
accompanied by many smaller birds and by untold millions of 
flies and gnats, evidently living upon the decaying animal matter, 
which is abundant and offensive. 
The vegetation was found to be a strange mixture of shore and 
forest plants, the latter in spite of the bareness of the islands includ- 
ing some that habitually grow in deep shade. There were also 
other species which belonged to neither category. Wherever con- 
ditions favored accumulation, humus was deep and seemed to be 
composed largely of the remains of Calamagrostis canadensis, the 
most abundant species upon the islands. In some places this 
grass formed a thick rank growth, flowering abundantly. Over 
large areas there was merely a short turf, and in many places the 
humus was entirely bare, doubtless kept so by the gulls in their 
domestic operations. With Calamagrostis and forming a thicket- 
like growth was found Pyrus americana, and this was the only tree 
upon the islands. It was most abundant upon the upper part of 
the beach mentioned above, where a few specimens were noted 
4 that were 4 m. high and 1.5 dm. in diameter (fig. 29). There were 
_ more dead specimens than live ones, and the living showed the 
effects of the hard conditions in yellow and curled foliage and 
dead branches. Fruit was borne abundantly. Other shrubs that 
_ formed a part of the thicket were Salix phylicifolia L.; Cornus 
____Stolonifera Michx. (red osier dogwood); Ribes prostratum L’Her 
- (fetid currant), fruiting in wonderful abundance; R. oxyacanthoides 
L. (prickly gooseberry); Rosa acicularis Lindl. var. Bourgeauiana 
Crépin; Rubus idaeus L. var. aculeatissimus (C. A. Mey.) Regel & 
Tiling (red raspberry), abundant; Sambucus racemosa L. (red- 
_ berried elder); Taxus canadensis Marsh (ground hemlock), fre- 
quent, forming a low matted yellowish growth partially protected. 
late a a 
