ROOT HABIT IN THE FAR NORTH 227 



of the frozen soil; furthermore black spruce grows with frozen 

 soil but 8 cm. below its roots. The temperatures about the roots 

 in this latter situation were between 33° and 35°F. in August. 



The particular plant figured was found in the deep, sandy soil 

 near the Brule river in northern Wisconsin, a situation favoring 

 deep root formation. The figure is considerably simplified for 

 the plant forms a mat of fine, interlacing roots, the two longest 

 being figured without horizontal branches. 



Black spruce also grows on rocks so nearly bare that the trunks 

 are only kept upright by the mutual interlacing of roots of neigh- 

 boring trees. In crossing portages near the headwaters of the 

 Kawakashkagami river n northern Ontario the author has 

 observed that where smoldering moss fires had burned the inter- 

 lacing roots of the spruces, the unscorched trunks, deprived of 

 their only support, were falling in every direction. In Sesegenega 

 lake in the course of the same river, the black spruce grows on 

 rocky islands. The supporting mat of roots is so thin and dense 

 that one may cut through it down to the rock in a semi-circle 

 facing the lake and drag the enclosed body of small trees out on 

 the surface of the water, where they will float for some time in 

 an upright position. 



The consideration of black spruce may be closed by noting that 

 the shallowness of the root system of a species is not, of course, 

 an infallible guide to the extent of its northerly distribution. 

 The root habit is but one of the characteristics that must be taken 

 into consideration in accounting for distribution in the north. 

 Black spruce, for example, has a shallower root system than 

 white spruce and grows in soils too shallow to support white 

 spruce. Yet at the northern limit of its range black spruce is 

 practically a shrub (Doobaunt lake (63°N. lat. 102°W. long.), 

 Kath-Kyed lake (62°45'N. lat. 98°W. long) while white spruce 

 is a fairly large tree.'' Beyond the mouth of the Nelson river 

 black spruce is replaced in the cold swamps along the shorj of 



^ Tj^rrell, J. B., Report on Doobaunt, Kazan and Ferguson rivers and the 

 north-west coast of Hudson Bay. Ann. Rep. (New Series) Geol. Survey Canada, 

 Vol. 9, pp. 1F-219F. 1897. (J. W. Tyrrell was plant-collector on this ex- 

 pedition.) 



