126 BOTANICAL GAZETTE [FEBRUARY 
very effective as a conserver of moisture. When the soil elsewhere 
is absolutely dry, that beneath a layer of Arctostaphylos is often 
found still to contain a high percentage of water. 
Vaccinium pennsyluanicum becomes of importance soon after 
the establishment of the mat, and frequently dominates large 
areas in which the junipers and Arctostaphylos appear as relicts 
only. 
It must not be understood that there is a distinct belt of heath 
mat along the entire front of the forest, or even that it is commonly 
found continuously over very large spaces. It usually occurs in 
patches more or less united, separated by areas of bare .or incom- 
pletely covered rock, and with scattered trees, invaders from the 
forest, growing upon it. Telescoping of stages is very pronounced 
in the rock shore succession, so that in a limited area we frequently 
find representatives of the earliest pioneers, the climax forest, and 
of all stages between. 
5. The jack pine-black spruce stage and the establishment of the 
climax forest.—It seems clear that the climax forest often follows 
immediately after the establishment of the heath mat. It seems 
equally certain that in many places a relatively xerophytic forest 
stage intervenes, in which the species are Pinus Banksiana Lamb. 
(jack pine) and Picea mariana (Mill) BSP (black spruce). Populus 
tremuloides Michx. (aspen) is also sometimes present. The condi- 
tions which determine the presence or absence of this stage were 
not discovered. In either case the establishment of the forest 
consists simply in a gradual increase in the number of trees inhabit- 
ing the rocky shores, the early advance being principally along 
the crevices. 
The jack pine-black spruce forest is at the present day rather 
limited in extent. It was observed in its best development along 
the southeast coast of the island from the region of Laké Whittlesey 
to Lea Cove, and along the northwest shore of Rock Harbor for 
several miles. In other localities transitional stages passing into 
the climax were seen. Where conditions are most xerophytic 
Pinus Banksiana is dominant. In such places the trees grow far 
apart and there is much bare rock visible between them. Cladonias 
are the characteristic ground cover, C. rangiferina, C. sylvatica, and 
