LYSICHITON CAMTSCHATCENSE (l.) SCHOTT I99 
forest on the various peat bogs of the region are the following: Picea 
sitchensis, Pinus contorta, Pinus monticola, Thuja plicata, Pseudotsuga 
taxifolia and Tsuga heterophylla. Only three of them are important, 
namely: Pinus contorta, Thuja plicata and Pseudotsuga taxifolia. 
Picea sitchensis and Pinus monticola have a very limited distribution 
in this region. Their occurrence in peat bogs is probably due to 
lessened competition in the latter localities enabling these species to 
persist in a region not otherwise favorable to their development. 
The occurrence of Pseudotsuga in the Green Lake bog, discussed in 
detail below, is likely to be attributed to the partial drainage of that 
bog, Rigg (21). Of the remaining, Pinus contorta and Tsuga hetero- 
phylla are especially worthy of notice. Tsuga is alw^ays confined to 
the youngest and wettest peat bogs, in fact, it is the first conifer to 
appear when the Sphagnum has become firm enough to support trees. 
When the sphagnum bog gets older and drier Tsuga is killed. The 
many dried up trunks of Tsuga in older peat bogs or in older and 
drier parts of a peat bog are remnants from a younger and wetter 
stage in the history of the bog. The bog forest of the sphagnum bog 
in its dried stage is a pure growth of Pinus contorta. This tree is 
confined to dry hills and gravelly prairies outside of peat bogs. The 
occurrence of a plant both on peat soils and on dry, sandy soil has 
repeatedly been observed in America as well as in Europe and Dach- 
nowski (9) has recently added new examples to the list. 
It follows that the relative age of the bog can be determined from 
the nature of the bog forest. The bogs of Mud Lake with Tsuga 
and the Crystal Lake bog with Pinus contorta are illustrative examples. 
The position of Thuja plicata with regard to its resistance to dry- 
ness seems to be between that of Tsuga and Pinus contorta. In 
eastern Washington and in the Puget Sound region it occurs on dry 
xerophytic slopes as well as in swamps thus showing the same indif- 
ference to habitat as in the Chicago region (Cowles, 6) and approaching 
in nature Pinus contorta. It is not common in the peat bogs of the 
region (Mount Constitution), but occurs in bogs partially drained. 
It is through the two above mentioned stages in the bog forest, 
the Tsuga association and the Pinus contorta association, that the 
climax forest will be reached. More extensive investigations have to 
be undertaken before the course of development after the pine as- 
sociation can be ascertained. As the xerophytic conditions decrease 
a forest composed of Tsuga and Thuja will in all likelihood establish 
itself and conclude the series of successions. 
