RATE OF GROWTH IN SPHAGNUM BOGS 727 



lock (Tsuga hctcrophylla Sarg.)- I" one case, however (Maltby bog), 

 there is a nearly pure stand of lodgepole pine (Pinns contorta Dougl), 

 and in some portions of the Henry bog there is a nearly pure stand of 

 western white pine (Pintis monticola Dougl.). Other conifers found 

 in sphagnum are giant cedar (Thuja plicata Don.), the Sitka spruce 

 (Picca sitchcnsis Carr.), and the Douglas fir (Pscudotsuga taxifolia 

 Brit.). 



The advancing forest is always related to the forest of the Puget 

 Sound region in general. The coniferous species mentioned above are 

 all commonly found in the forests of the region, and each one may be 

 the dominant element of the forest on certain areas. The Douglas fir 

 is the commonest conifer of the region. In certain cases, however, the 

 bog forest is not related to the forest found upon the bordering "hard" 

 land. For instance, the lodgepole pine, which is so common in the 

 Maltby bog, is certainly not at all common in the neighboring forest, 

 and if it is there at all it has escaped the observation of the writer. 



In no case has a bog been found where the forest stage has advanced 

 far enough to drive out the characteristic bog flora, such as Labrador 

 tea (Ledum grocnlandiciim Oeder), swamp laurel (Kalmia polifolia 

 Wang.), and cranberry (Oxycoccus oxycoccus intcrmedius Pip.). The 

 nearest approach to such a condition is in the Green Lake bog, which 

 surpasses all others examined in both the number of species of trees 

 and the number of individuals. This can hardly be regarded as typical, 

 since the present bog is only a small portion of the original one and is 

 drained by ditches on two sides. The main part has been cleared, 

 drained, and scalped and is now under cultivation as gardens. 



It is quite possible that in many cases a bog succession has preceded 

 the present forest in some portions of this region. This would seem 

 especially probable in the case of cedar swamps. The writer has not 

 investigated the substratum in any of these. However, late stages of 

 forest succession, where any evidence of bog vegetation still remains, 

 do not seem to be evident in the portions of the Puget Sound region 

 visited by the writer. 



The only deciduous trees that the writer has found in Puget Sound 

 bogs are the red alder (Alnus oregona Nutt.), the bog willow (Salix 

 myrtiUoides L.), and the western dogwood (Cornus occidentalis Gov.). 

 Even these are rare. On the borders of one bog (Mud Lake bog), 

 where it is advancing on the open water of the lake, the peat-bog birch 

 (Betiila glandnlosa Michx.) is very common, but it is evidently a pio- 

 neer along with Labrador tea and swamp laurel in the formation of 

 the bog stage and is not to be regarded as an invader of the bog. 



