46 The New York State College of Forestry 
normally rhizomatous stems, and by the upward growth of 
sphagnum among foliage bearing stems, thus investing them in 
a constantly wet but porous blanket, stimulates active root 
development along these stems and thus each branch becomes 
potentially a new plant. This leads to the development of 
expanding shrub colonies, especially of heath species, promotes 
the succession of heath shrub upon sedge meadow and accounts 
for the spotwise occurrence of these shrub colonies. This layer- 
ing method of reproduction in black spruce seems at least in 
part to account for the dominance of this species in many 
Adirondack bogs. 
10. The interactions of growth between sphagnum and the 
vascular bog plants, although in the nature of communal adjust- 
ment, is in reality a competition for advantage of position and 
exposure. It appears that the vigorous upward growth of 
sphagnum takes place especially in September and October at 
low temperature after the shading effect of vascular plants has 
been reduced by leaf fall. The compensating growth of vas- 
cular plants occurring of course during the following growth 
season. The special aspect of vegetative propagation from 
stems imbedded by the upward growth of sphagnum (layering) 
is associated with this phenomenon. 
11. A comparison of different sand plains associated with 
the Adirondack region indicates a very close correlation between 
the vegetation ‘sequences and the drainage conditions. Cer- 
tain edaphic conditions due to sand deposits of this nature are 
common to all as shown by the occurrence of certain identical 
or ecologically similar species in each, but the height of the 
water table in connection with a small degree of unevenness of 
surface due to wind and water erosion determines a series of 
different association complexes from typical bog in the low 
lying undrained plain, to semi-marsh meadow and willow-alder 
associations devoid of sphagnum, to low lying but dry heath 
with Polytrichum and Cladonia rangiferina apparently replac- 
ing sphagnum in the pioneer stage, finally to pine heath, in 
the sense defined by Harshberger. (9) 
