4, BULLETIN 820, U. S. DEPARTMENT OF AGRICULTURE. 
origin developed by the weathering of the underlying rock. This is 
the “Great Laurentian Shield,” which comprises over 50 per cent of 
the area of Canada and extends from the northwest arm of the Lake of 
the Woods, northwestward and northward to the mouth of the Mac- 
FIGuReE 1, 
DISTRIBUTION OF 
JACK PINE 
“Commercial Range 
i Botanical Range 
kenzie River, the Arctic Ocean, and the mouth of the Winnipeg River, 
and eastward through Ontario, Quebec, and Labrador. (See fig. 1.) 
Lakes, rivers, and swamps alternate with low hills and plateaus, which 
show a remarkably even sky line. The network of waterways extends 
throughout the region. The soil is found mostly along stream 
valleys (alluvial), on the southern exposures of ridges (glacial sands 
