1913] COOPER—ISLE ROYALE 231 
very dense growth, and through its shading power and ‘he great 
amount of waste that falls from it finally eliminates the lower 
shrubs and ‘stops the upward growth of the moss. 
The bog trees, Larix, Thuja, Picea mariana, usually follow the 
sphagnum when it is present. When it is lacking they start upon 
the sedge mat with the shrubs. The climax trees enter very soon 
after or often actually with the bog trees, so that pure bog forest 
is practically absent. The bog trees die out because they are 
intolerant of shading, and the climax forest results. 
Telescoping of stages is prominent throughout the late history 
of the succession. 
The reason for the early establishment of the climax forest is 
found in the likeness between the bog soils and those of the forested 
uplands, the latter being almost as peaty as those of the bogs. It 
follows that whatever trees can grow upon one soil may also exist 
upon the other. 
The delta swamp succession 
Delta deposits are found in most of the sheltered bays where 
Streams enter from the upland. 
The succession of vegetation upon these deposits passes through 
the following stages: (1) aquatics; (2) sedges; (3) grasses (Calama- 
grostis canadensis most important), which form broad meadow-like 
growths and produce a limited amount of peat; (4) shrubs, among 
which Myrica Gale and Alnus incana are most important; (5) swamp 
forest, made up of Thuja occidentalis, Larix laricina, and Fraxinus 
nigra, the first being dominant; (6) climax forest of Abies balsamea, 
Betula alba var. papyrifera, and Picea canadensis. 
There is a general likeness to the bog succession; among other 
points, in the early establishment of the climax forest after the 
coming in of the swamp trees. 
The important points of difference from the bog succession are: 
the firmly grounded sedge mat; interpolation of the grass stage; 
absence of sphagnum, bog shrubs, and Picea mariana; dominance 
of Thuja in the swamp forest. 
Intermediate conditions between the two successions occur, and 
actual transition from delta swamp to bog succession occasionally 
takes place. 
