THE CLIMAX FOREST OF ISLE ROYALE, LAKE 
SUPERIOR, AND ITS DEVELOPMENT. II 
_ CONTRIBUTIONS FROM THE HULL BOTANICAL LABORATORY 165 
WILLIAM S. COOPER 
(WITH SIXTEEN FIGURES) 
Part II.—The successions 
THE PRIMARY SUCCESSIONS 
The xerarch successions 
I. Physiographic development of the habitats and description 
of present shores 
The physiographic development of the shore habitats is in large 
part that of the island itself, which has been briefly outlined in the 
introduction. Since the postglacial history of Isle Royale has been 
one of gradual emergence from the waters of Lake Duluth and its 
successors, it follows that all parts of the island have at some stage 
of the process been shore. 
The present shores of Isle Royale may be classified in several 
ways. First, there are the rock shores and the beaches, of which 
the former are vastly the more important. The rock shores may 
be classified in three ways: according to degree of slope, degree 
of shelter, and kind of rock involved. According to slope we find 
two classes: cliff shores and gently sloping shores. These two 
types are usually sharply distinguished. The cliffs are character- 
istic of the northwest coast of the island and of its surrounding 
islets, being produced by the broken edges of the lava and sedi- 
mentary layers; while on the southeast coast, the slope of the 
shores corresponds rather closely with the dip of the rocks, which 
is nearly everywhere gentle, averaging perhaps 10-15°. The cliffs 
range from 1 to 20 m. or more in height, are frequently perpendicu- 
lar, and may sometimes be seen to descend without a break to 
considerable depths below the surface of the water. According to 
degree of exposure the shores, both cliff and sloping, may be divided 
115] [Botanical Gazette, vol. 55 
