1913] COOPER—ISLE ROYALE : Igl 
II. Vegetational development in the bog habitat — 
1. Channel-bay stage 
Even as early as the channel-bay stage we find the beginnings 
of the vegetational history of the bog habitat. If the body of 
water be large or subject to considerable wave and current action, 
plant life is practically absent. In sheltered places, however, 
there lives a plant society, sparse but characteristic. The com- 
monest species is [soetes macrospora Dur. (quillwort), growing 
entirely submerged at a depth of o.3-1m. in the silty sediment 
that covers the bottom. Jsoetes here attains an unusual size, the 
crowns being frequently 5 cm. and more in diameter. With it 
grow occasional plants of Chara (stonewort), Ranunculus aquatilis 
L. var. capillaceus DC (water crowfoot), Potamogeton perfoliatus L. 
and other spp. (pondweeds). On shoals and along the reefs at the _ 
ends of the narrow islands and points are frequent clumps of sedges: 
Carex aquatilis Wahlenb., C. stricta Lam., C. lenticularis Michx. 
2. Lake stage 
The lake stage is considered as extending from the first complete 
inclosure of the body of water to the time when the bog’ vegetation 
has brought about its extinction. During this physiographic 
stage all the vegetational stages of the bog succession usually 
appear in their accustomed order. The aquatics are already 
present and the sedge society has often made a slight beginning. 
The latter now develops with rapidity, especially in the smaller 
lakes, and is followed in turn by the sphagnum-shrub society and 
the bog forest. 
; a) Peat formation 
Peat formation in the northern and southern peninsulas of 
Michigan has been described by TRANSEAU (56) and by Davis 
(19). The bogs which Davis studied, especially in the Upper 
Peninsula, are very similar to those of Isle Royale, and this author 
shows that the sedge mat is the most important agent in the forma- 
tion of the peat. Lack of time and facilities prevented a study of 
the basin-filling process upon Isle Royale, but it is certain that 
the bulk of the peat is deposited through the formation and sinking 
of the sedge mat and the accumulation of finely divided material 
