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GOTE TURESSON 
f 
place of the former marginal successions and typical peat bogs are 
built up. In the Puget Sound region where a young topography and a 
moist climate favor the development of peat bogs, two different types 
can be distinguished, the second type deviating from the first one 
in so far as the sedge stage has been eliminated. In other respects 
the parallelism between the two types is perfect. Both arise and 
develop from an initial hydrophilous vegetation, both reach the fatal 
stage inaugurated by the ingress of Sphagnum and, finally, both 
culminate in the coniferous climax forest. 
For an illustration of the first type we may take one of the numerous 
bogs on Mount Constitution in the San Juan Islands. This particular 
one is situated in a pocket in the mountain and is about 8 hectares in 
extent. There is open water in the central parts and a hydrophilous 
vegetation composed of Menyanthes trifoliata, Nymphaea polysepala, 
Polentilla palustris and Char a. Encroaching upon this vegetation 
and occupying most of the peripheral parts of the bog we have a 
typical sedge bog meadow (Dachnowski 8, 9), the low moor, grass 
moor or sedge moor of Warming (28) mainly composed of Carex. 
The ground stratum is made up of Hypericum anagalloides and mosses, 
notably Hypnum giganteum. The field stratum has the following 
herbs in addition to the Carex species: Galium triflorum, Mentha 
canadensis, Menyanthes trifoliata, Potentilla palustris, Scutellaria 
galericulata, Veronica scutellata, Viola palustris and in spots Lysichiton 
camtschatcense. A thick soft mass of Sphagnum occupies a small 
area in the middle of the bog bounding the open water vegetation. 
This supports the typical sphagnophilous plants of the region: Ledum 
groenlandicum, Kalmia glauca, Oxy coccus oxy coccus intermedins and 
Drosera rotundifolia. In places where the sphagnum has been killed, 
for reasons to be discussed later on, Philonotis fontana has stepped 
in and maintains the same characteristic plants as sphagnum in- 
cluding Drosera rotundifolia. That the sphagnum is spreading and 
will ultimately supplant the sedge vegetation is evident from the fact 
that small colonies of it have succeeded in establishing themselves 
among the sedges in advance of the main mass. Seedlings of Pinus 
monticola and Thuja plicata are common among the sedges, and dead 
trunks of Tsuga heterophylla, discussed more in detail below, are 
frequently met with. 
The factors that condition the development of the second type 
1 I am indebted to Professor T. C. Frye for the determination of the mosses. 
