VOLUME LXVI NUMBER 6 
THe 
BOTANICAL GSAZETTE 
DECEMBER 1918 
LIMITING FACTORS IN RELATION TO SPECIFIC 
RANGES OF TOLERANCE OF FOREST 
TREES 
A. H. HUTCHINSON 
(WITH SEVEN FIGURES) 
The conclusions recorded in this paper are drawn from a study 
of the forests throughout the Province of Ontario, particularly 
along the shores of Lake Ontario, Lake Simcoe, the Kawartha 
Lakes, and Rideau Lakes; in Algonquin Park and in Mattagami 
and Timagami Forest Reserves. Observations, with notes, have 
been made during more than 6000 miles of travel by canoe and over- 
land through the forest country of northern Ontario, especially 
along the streams and lakes forming the headwaters of the Muskoka, 
Maganatawan, Petewawa, and Madawaska rivers; also of the 
Montreal, Sturgeon, Wanapitei, Vermilion, Mattagami, and Abitibi 
rivers. While the greater part of the discussion has particular 
reference to Ontario, the conclusions are made in the light of some 
personal knowledge of the forests southward to the Gulf of Mexico 
and westward to the Pacific. 
The data regarding the limits of forest trees recorded in the 
accompanying maps have been obtained principally from accounts 
of the explorations of BELL (2), Macoun (19, 20), and Low (18). 
The records of isotherms and precipitation areas have been copied 
from the Geological Atlas of Canada, 1915. So far as the writer 
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