232 HOWARD E. PULLING 



lat., 101 °W. long.) about 240 miles within the Barren Lands. 

 On the coast of Hudson Bay it replaces black spruce in the wet 

 swamps. Whether these swamps are bogs is, however, uncertain. 



It would seem that the root habit of white spruce should be 

 classed as rather flexible, for it is very shallow rooted in thin 

 soils. 



Balsam Poplar {Populus balsamifera L.) maintains several 

 trees on the same general root system, as indicated in the figure 

 in which all were over twenty-five years old. These (and pre- 

 sumably there were others growing on the same root system) 

 were a few meters distant from the white birch, described above. 

 In spite of many attempts, no young trees were found, each small 

 tree being but a branch of a larger one some distance away. The 

 general habit of the roots is indicated n the figure, although only 

 one is shown. These roots penetrate a short distance vertically 

 and then send horizontal branches which sooner or later repeat 

 the process until impenetrable soil is reached. These roots are 

 often found very close to the frost line. It would seem, from the 

 general appearance and the habitats that this root system is a 

 more or less flexible one, but one that can never live in such 

 shallow soils as the white spruce can thrive in. J. W. Tyrrell 

 found it no farther north than the north shore of lake Athabasca 

 (about 59''40'N. lat., 109-1 10°W. ong.) over 150 miles south 

 of the Barren Lands. 



White Pine {Pinus strohus L.) is essentially a deep rooted 

 form. Its tap root penetrates vertically with few far-reaching 

 laterals. Another feature that seems to be noteworthy is the 

 characteristic bunching of the roots so that but a small horizontal 

 area is covered. It may be this characteristic that prevents its 

 establishment in dry soils where a germinating seed is dependent 

 upon surface water. This individual was taken in the deep, 

 sandy soil near the Brule river. It is never found very far 

 north of the height of land separating the lake Superior from the 

 Hudson Bay drainage. 



