14 BOTANICAL GAZETTE [JANUARY 
Above the general level of the treetops tower occasional very old 
white spruces, conspicuous features in spite of or rather on account 
of their fewness. The paper birches make considerable show by 
reason of their thick tops, often appearing to compose at least half 
of the forest, but in reality not much more abundant than the 
spruces. The balsams are plainly very abundant, and are actually 
even more so than they seem, since many small ones are hidden by 
other trees. There are a few large specimens approaching the 
spruces in size, and thick groves of medium-sized trees are just 
Fic. 2.—Exterior view of the climax forest upon one of the row of islands bound- 
ing Rock Harbor on the southeast: two tall white spruces at the right; a group of 
balsams at the left; several large birches. 
visible, their spirelike tips appearing in dense clusters among the 
birch tops. The forest toward the harbor is bordered by a belt 
where Alnus crispa (Ait.) Pursh (green alder) is common, filling 
in the gaps between the trees. In this region Pyrus americana 
(Marsh) DC (mountain ash) is also frequent, and Thuja occidentalis 
L. (arbor vitae) is occasional. 
Upon entering the forest we seem in many slice to be in the 
midst of a dense growth of nearly pure balsam. The individuals 
of this species are of all sizes, and there is a pronounced tendency 
among them to grow in close groups. The small trees (roughly 
