26 The New York State College of Forestry 
wet sponge more aggressively than in the case of black spruce, 
since, of course, tamarack lacks the compactness of form and 
the opacity of foliage which tend to retard or suppress the 
sphagnum encroachment noted in the former species. Tama- 
rack, moreover, loses its foliage at the season when sphagnuni 
was observed to make its greatest gains and in this respect 
appears to be threatened with suppression by the sphagnum 
blanket as black spruce is not. A compensating feature appears 
to lie in the more rapid height growth of tamarack, its slender 
spire contrasting with the spreading habit of black spruce at 
the period of invasion of the sphagnum-shrub association. 
The critical stage for the conifer species is, of course, that 
in which seed germination and the establishment of the young 
seedlings take place. The whole question of the time when 
the vegetation sequence proceeds in the direction of conifer 
forest rather than remaining static as a closed sphagnum-shrub 
association turns on this. Unfortunately as had to be admitted 
before in discussing the pioneer stage of shrub invasion of the 
sphagnum sedge association, data are lacking notably in find- 
ing seedlings of the current year or very young conifer plants. 
It is evident however that the chances of germination and 
establishment of the conifer seedling are increased as the gen- 
eral bog surface becomes diversified by being broken up into 
mounds with dense shrub and slopes and depressions of 
exposed sphagnum. In its most vigorous and apparently 
earlier stage the shrub stand may become very compact and 
continuous. See figure 10. In such a zone there are obvi- 
ously fewer chances for conifer seedlings to secure a start and 
no specimens of conifers have been noted in this zone although 
it lies adjacent to the area now being invaded. 
(b) The Closed Stand of Young Black Spruce and Tamarack 
Forest. This expression refers to the stage at which conifer 
species have closed in over the bog but have not lost their 
lower branches by crowding and shading. There is not yet 2 
closed canopy with its under story of more or less clear boles, 
Figure 18. The northern end of the main bog and the greater 
part of the western section of it have reached this stage. As 
