GOTE TURESSON 
support for the Sphagnum and its associates. In Lake Kapowsin, 
near Tacoma, logs floating in the water have taken the place of the 
floating mat, and Drosera rohmdifolia, Kalmia glauca and other bog 
xerophytes flourish in the thin layer of humus covering the logs.^ 
When the rolling sphagnum cover has reached out to the open 
water bounding the floating mat it plunges down in the water by 
continual growth from behind thus filling in the pond. This may be 
seen in many places, for instance, at Mud Lake, Echo Lake and Crystal 
Lake (compare also Dachnowski, 7, Eriksson, 10). In the latter 
locality it also succeeds in building extensive mats out into the lake 
supported by the branches of Ledum groenlandicum (compare here 
Gates, 11). 
Some additional facts may be brought out with regard to the 
various stages in the peat bog vegetation of the region. It is clear 
that smaller deviations may occur from the development of the two 
types described in the above. The bog shrub stage, which in this 
region precedes the bog heath stage, may be wanting or but poorly 
developed. It is represented by Spiraea douglasn in a bog near 
Maltby. There is also some difference in the composition of the 
bog forest. The relations of this stage to the climax forest is some- 
what difficult to determine as the actual nature and composition of 
the climax forest is still a matter of conjecture. The demineral- 
ization of forest soil due to the humid climate, and the rapid accumu- 
lation of humus over the mineral soil layer favor the growth of Tsiiga 
heterophylla and Thuja plicata while it hinders the development of 
Pseudotsuga taxifolia which thrives best on mineral soils. L^ndoubted- 
ly, Tsuga and Thuja would together dominate the lowland region 
of the mainland were it not for the extensive forest fires which by 
destroying the humus mantle prepare the soil for Pseudotsuga. The 
belief that the latter tree is excluded from the culminating type of 
forest vegetation is further strengthened by the fact that Pseudotsuga 
is unable to seed under its own shade while seedlings and young trees 
of Tsuga and Thuja are common in the mature Pseudotsuga forest. 
With these points in mind the question of the relation of the bog 
forest to the climax forest, here supposed to be composed of Tsuga 
and Thuja, will become clearer. The conifers making up the bog 
1 Rigg {22) calls attention to the noteworthy fact that Drosera rotundifolia, one 
of the most typical sphagnophilous plants, occurs outside of the sphagnous sub- 
tratum in this locality. Its occurrence on a Philomatis fontana carpet on Mount 
Constitution, already referred to, becomes of interest in this connection. 
