LYSICHITON CAMTSCHATCENSE (l.) SCHOTT 
203 
of fallen foliage suppresses the growth of Sphagnum, Oxycoccus and 
similar plants. The following is a quotation from Cooper (4) : ''Be- 
cause of the shade which Ledum produces and the considerable amount 
of waste which falls from it, the upward growth of the moss is grad- 
ually retarded and finally ceases altogether. About this time or 
often before, young plants of other mosses more or less tolerant of 
shade become established upon the higher parts of the Sphagnum 
moss. Polytrichum s trie turn, Aulacomnium palustre and Calliergon 
schreberi soon follow. These species form mats of continually in- 
creasing lateral extent which put an effectual stop to further upward 
growth of Sphagnum." The same facts are brought out in another 
paper by this author (Cooper, 5). Similarly, Raunkiaer (20) calls 
attention to the harmful influence of the shady spruce forest on the 
Sphagnum bog as well as to the injurious effect of leaf fall on Sphagnum. 
The best illustration of the sensitiveness of Sphagnum to shade is 
given by Eriksson (10) in his studies on the peat bogs in the middle 
part of Sweden. It may be cited here. If a spruce has succeeded 
in establishing itself on top of a Sphagnum hummock in the bog it 
will ultimately be killed. As Sphagnum is unable to grow in the 
dense shade below the spruce a depression is formed here. This 
depression becomes filled with water which results in the death of 
the tree. Similar '' Beschattungs-Schlenken" have prior to Eriksson 
been described and explained by Sernander (vide Eriksson). 
When viewed in the light of these additional data it is easy to 
see how the deep skunk cabbage pits in the Green Lake bog originated. 
Sphagnum is unable to grow in the dense shade cast by the large 
skunk cabbage leaves during the vegetative season. In late fall 
when the leaves rot, an area all around the plant becomes covered 
with a thick layer of decaying leaves which smothers and mechanically 
injures the Sphagnum if it has succeeded in encroaching upon the 
area dominated by the skunk cabbage. In this way the Sphagnum 
is kept at a distance, and the pit deepens as the Sphagnum layer 
continually thickens in the edges not in reach by the skunk cabbage. 
Finally mosses more tolerant of the deep shade and waste gain en- 
trance and form mats on top of the Sphagnum in the way described 
by Cooper. 
A few additional instances from this region of the sensitiveness 
of Sphagnum to waste and shade may be cited. It was stated above 
that Sphagnum had been killed in certain places of the Mount Con- 
