in fig. 13* The vectors DA, AB, and BC # (upper figure) , 
illustrate the effective response of the three principal 
species somewhere up the north slope. Evidently the 
magnitude of the vectors does not correspond to the number 
of individuals of each species; in other words, while 
population may indicate response, it is not a measure of 
it. The vector CD indicates the effective control of all 
other species. The lower figure illustrates the conditions 
of balance near the top of the ridge. If any one species 
were eliminated from the forest, it would soon come back 
in approximately the some proportion at any point. 
C. Successions leading to the hemlock climax. 
1. Primary successions. 
The primary successions leading to the 
hemlock climax may be seen along the shore of Lake Superior, 
at the foot of the first range. The pioneer stages are 
present in most cases, but the transition is often rather 
abrupt. Lack of well marked zonation is probably due to 
the severe conditions along the shore. 
a. Physiographic influences. 
The development of the shore line is 
correlated with the post-glacial history of the Lake Superior 
region. On account of the gradual withdrawal of the lake. 
