12/ BOTANICAL GAZETTE [JANUARY 
II. Hydrarch successions 
1. The bog succession 
2. The delta swamp succession 
B. Secondary succession 
The burn succession 
4. MAINTENANCE OF EQUILIBRIUM.—It has been possible to 
state with brevity the three points that have so far been presented; 
indeed, to one visiting the island they are almost self-evident. The 
validity of the fourth is not so plainly to be seen. 
Both observational and experimental studies have shown that 
the balsam-birch-white spruce forest, in spite of appearances to the 
contrary, is, taken as a whole, in equilibrium; that no changes 
of a successional nature are taking place within it. Superficial 
observation would be likely to lead to exactly the opposite conclu- 
sion. In the presence of the other good evidences of permanence 
outlined in the preceding paragraphs, it became necessary to seek 
for an explanation of the seeming condition of rapid change that was 
apparently so plain in the forest. The solution was found in the 
course of a detailed study which included (1) the characteristics 
and life history of each tree species and of certain of the lower 
forms which were of importance, and (2) all the processes and 
changes brought about through the interrelations of the forest 
species, discovered by intensive study of a number of limited areas 
of definite size (quadrats), with every available source of evidence 
laid under contribution; in other words, an attempt at a thorough 
investigation of the dynamics of the forest. In the following dis- 
cussion the results will be given under three heads: I. Description 
of the forest; II. Studies of individual species; III. Quadrat 
studies. 
I. DESCRIPTION OF THE FOREST 
For the sake of concreteness I have selected a definite locality 
for description, bearing in mind, however, that such a thing as a 
piece of forest of limited extent which is “typical” of the growth of 
a region hardly exists. 
Smithwick Island (sec. 4, T. 66 N., R. 33 W.) was the selection 
for this description and for particular study, because the outer 
row of small islands inclosing Rock Harbor had the appearance of 
a i al ata a 
Pee ee Oo ae 
