Forest Development in the Adirondacks 21 
progress of shrub invasion from an occasional plant or colony 
to a closed shrub association. In general, the south one-third 
of the main marsh may be described as a complex of pure 
sphagnum-sedge and sphagnum-sedge-shrub associations with 
sedge predominating; the middle third as an association com- 
plex varying from a bare predominance of shrub to a closed 
sphagnum-heath shrub association, while the northern third 
is a complex of sphagnum-shrub-conifer with conifers pre- 
dominating at the northerly boundary. (Figure 15.) 
Method of Development. The energy and rapidity with 
which the shrub elements invade the sedge association would 
lead one to expect to find abundant examples of shrub seedlings 
or individual plants recently established. Repeated examina- 
tions have however not borne out this expectation. Small young 
plants of Chamaedaphne and other shrubs may be found, but 
in the main the original plant has become a clump or colony 
by its rapid vegetative propagation under the sphagnum. Con- 
ditions for the germination of seed and establishment of the 
invading shrubs would appear to be favored by the creation of 
sphagnum mounds in the sedge zone. In any event, when a 
shrub gains foothold the interaction between sphagnum and 
shrub — the race to avoid suppression as it would seem,— 
results in building up a higher mound of sphagnum which in 
turn leads to a more vigorous vegetative expansion of the shrub 
colony for here as will also be shown for the invading conifer 
zone, the moist sphagnum stimulates a most vigorous develop- 
ment of shoots and of abundant roots from these which in effect 
(and in black spruce actually) is rapid reproduction by 
layering. Thus it comes about that the shrub colonies and the 
sphagnum-shrub mounds which their interaction creates 
increase rapidly in height and especially in diameter so that 
progress is rapid toward a complete dominance of sphagnum- 
shrub vegetation as well as in building up the surface of the 
bog. Figure 12 shows a dissection of a mound formed by 
sphagnum and Chamaedaphne. The spreading shoots of the 
shrub appear all to be related to a single original plant. The 
sand substratum is shown. There appears to be no growth of 
