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GOTE TURESSON 
of peat bogs in which the sedge stage is omitted are the same as those 
of the first type, and they may all be referred to the lack of drainage. 
Just why the sedge stage is omitted is not altogether clear. The 
best example of the type in this region is that of Mud Lake. This 
lake was once connected with Lake Washington but has in geologically 
recent times been separated from it by a sand bar thrown up by wind 
and wave action. Extensive sphagnum bogs occupy the upper end 
of the lake. These were very likely initiated while Mud Lake still 
was a bay of Lake Washington. The building up of sphagnum bogs 
on floating mat vegetation can easily be followed in the southern 
])ortion of the lake. Brasenia schreberi, Nymphaea polysepala, Pota- 
mogeton lonchites, P. NuUaUii, Utricularia vulgaris and U. minor are 
very important in shallowing the lake. Menyanthes trifoliata is here 
as in other places (Cooper, 4, MacMillan, 16) the important mat- 
former by virtue of its mass of intertwined rhizomes. Potentilla 
palustris invades the association, spreads, reaches the edges of the 
mat and advances out in the open w^ater. Fontinalis, aquatic Hyp- 
num species and other mosses solidify the mat, which next is invaded 
by Betula glandulosa and an undetermined Salix species. Sometimes 
also Spiraea douglasii appears in this stage and often but not always 
Typha latifolia. This is the typical bog shrub stage (Dachnowski, 
7, 8). The bog heath stage (Dachnowski, 7, 8) is initiated with the 
coming in of Sphagnum, which soon smothers the existing vegetation. 
The former shrubs are crowded out by Ledum groenlandicum and 
Kalmia glauca which together with Oxycoccus oxycoccus intermedius 
and Drosera rotundifolia establish themselves on the sphagnous sub- 
stratum. As the xerophytic conditions increase resulting in the 
drying up of the sphagnum bog in the middle and older parts there 
is again brought about a change in the composition of the flora. 
Ledum becomes stunted, disappears entirely from the central parts 
but persists in the edges bounding the open water. The same is in 
somewhat less degree true of Kalmia. Cladonia species and Erio- 
phorum chamissonis replace them. The bog forest (Dachnowski, 
7, 8), is advancing with scattered Tsuga heterophylla and seedlings 
of Pinus monticola as forerunners. 
The type of bog just described is by far the most common met 
with in the Puget Sound region. Indeed, the first type, distinguished 
by the sedge bog stage, is but poorly represented on the mainland. 
There is indication of such a stage in some places in Mud Lake and 
