1911] DACHNOWSKI—CRANBERRY ISLAND 27 
size and length to withstand the mechanical strains due to the 
action of air currents. The association is still an open commu- 
nity of plants and has four distinct vertical layers. The trees 
cast a relatively dense shade, in which grow seedlings and young 
trees of oak and maple, and a variety of shrubs and herbs. Most 
abundant are Sambucus canadensis, Impatiens biflora, I. pallida, 
Rubus sp., Dianthera ovata, Viola blanda, Aspidium spinulosum, 
Osmunda regalis, Carex scirpoides, Aspidium cristatum, Habenaria 
clavellata. 
There is protection from strong air currents, and in the changed 
light, heat, and moisture conditions the plants offer a striking con- 
trast to the vegetation next to be described. Many of the herba- 
ceous and shrubby species occur only sparingly, and are really 
constitutents of the other societies of the border zone. In the 
numerous maple and oak seedlings the evidences are seen that the 
Rhus-alder consocies will not continue to occupy the habitat. 
The lowering of the water table due to the continued addition 
of débris and leaf-humus will hasten the advent of better soil, 
drainage, and shade conditions. Almus and Rhus and their asso- 
ciates will find the new conditions unsuitable; they will disappear, 
leaving the zone more typically an oak-maple-ash formation. 
It is not probable that this coming society represents a climax 
forest for filled lake basins in this locality. There are limited 
portions on Cranberry Island which in the course of years are 
bound to revert to the central zone bog type, and that perhaps 
intermittently, for a settling and shrinkage of the numerous water 
pockets in the peat substratum will continue until all of the lower 
strata have become firm and compact. With continued accumu- 
lation of forest litter, the soil conditions will finally become drained 
and more xerophytic, to an extent that will constitute an ecologi- 
cal habitat considerably different from that existing in the neigh- 
borhood. Should the water level remain constant, the amount 
of upbuilding will be limited to the distance to which the water 
will rise through the accumulation of peat, and supply the growing 
plants at the surface with the necessary physiological water. 
It must not be assumed, therefore, that the development of a 
mesophytic forest could continue in the same direction indefinitely. 
