bo 
Or 
Forest Development in the Adirondacks 
the density of foliage and the opaqueness of it result in creat- 
ing a twilight zone beneath the single young spruce or its newly 
formed colony or clump such that the shrubs and the climb- 
ing mound forming sphagnums are gradually suppressed and 
finally largely eliminated. Thus one may find situations 
where the spruce has retarded or eliminated shrub and sphag- 
num growth so that while the general upbuilding of the spongy 
bog surface has continued all about, there will be underneath 
the clump a depression, which if the spruce were removed, 
would appear as an excavation one to two feet below the gen- 
eral level of the bog. Figure 17. Shrubs, if they still per- 
sist, will be found to send up shoots only around the margin of 
the spruce or more or less etiolated shoots through the gaps in 
the dense foliage. The bottom of the depression may continue 
to be occupied by living sphagnum, but this is strongly tolerant 
of shade and possibly represents the beginning of the 
sphagnum carpet which comes to occupy the shaded floor 
beneath the closed spruce stand. (See below under (c¢), and 
p. 37 under the role of sphagnum. ) 
The réle played by tamarack in the invasion of the snrub 
association of Grasse River Bog is rather secondary to that of 
black spruce, and this appears to be the case pretty generally 
in Adirondack bogs. However, tamarack is a constant if more 
seattered associate in the conifer invasion and in places estab- 
lishes pure stands. In bogs of the less extreme sort this species 
becomes the dominant conifer, but in a more extreme type, as 
for example the Bean Porid Bog (Bray [2], p. 125, and Fig. 
20) near Wanakena, tamarack is but infrequently represented 
while black spruce though much dwarfed persists in abundance. 
Contrasted with the secondary réle of tamarack in the invad- 
ing conifer stage and the young forest, is its prominence in 
the old bog forest as noted below. 
The habit of reproduction by layering in the case of tama- 
rack which has been reported by other observers (4) has, if 
it occurs in the Grasse River Bog, escaped my observation. 
There is apparently every condition present to favor this for 
the heavy sphagnum growth imbeds the lower branches in a 
