1919 ^^99^ ^^ ^^9 Sticcession 201 



the hardback thicket occurs a thick growth of Polytrichum juniperinum 

 instead of Sphagnum. Two specimens of aspen {Populus tremuloides) 

 grow in the central portion of the Spiraea-Sphagnum association near the 

 Carex-Sphagnum association. 



There were a few small cedar logs in this zone and the Carex- 

 Sphagnum zone. Aulacomnium sp. and two other species of moss grew on 

 these logs. The logs evidently float in winter and this fact accounts for 

 their flora. They had evidently floated to the situations in which they 

 were seen and their presence furnishes no evidence that a forest had ever 

 occupied this depression. The second zone occupied the portion of the 

 depression only slightly elevated above the first. 



A very well marked zone of aspen 10 to 20 m. (2 or 3 rods) in 

 width, occupies the beginning of the upward slope of this depression. 

 Those trees are mostly from 2.5 to 15 cm. (1 to 6 inches) in diameter. The 

 larger ones have a dense growth of foliaceous lichens on their trunks and 

 larger branches and many of the branches are dead. The younger trees 

 seem healthy. There is a good deal of hardback among the aspen and a 

 few scattered aspens grow in the outer portion of the Spiraea-Sphagnum 

 association so that the line of demarcation between the two does not seem 

 so sharp when one is in the area. It appears perfectly well marked, how- 

 ever, on looking down from the road near by. 



Sphagnum grows to a limited extent in a good many places among 

 the aspen trees, but the ground is much more generally covered by Poly- 

 trichum junvperinum. We may designate this as the Populus-Polytrichum 

 association. 



On the higher and comparatively level ground above and surrounding 

 the Populus-Polytrichum zone is what may be called the Psuedotsuga- 

 Gaultheria association, since the principal tree is the Douglas fir (Pseu- 

 dotsnga taxifolia) and the commonest shrub is salal (Gautheria shallon). 

 Young trees and even seedlings of fir are common right down to the 

 Populus-Polytrichum zone but not in it. There are a few young trees of 

 red alder (Alnus oregoiia) associated with the fir. The soil of this zone 

 is glacial deposit and is gravelly and, in places, stony. In some of the 

 more open places there is a good deal of kinnikinnick (Arctostaphi/los 

 uva-ursi). 



If this region remains undisturbed it is easy to foresee its natural 

 development into the sort of sphagnum bog that is typical of the Puget 

 Sound region. Indeed one may wonder why it has not already developed 

 into one. Three possible explanations occur to the writer as to why this 

 depressions is still in such an early stage of bog development. One is that 

 comparatively recent changes may have occurred in the drainage of the 

 region. Another is that the Sphagnum got a late start here. The third is 



