CAPPS: AGE OF THE LAST GREAT GLACIATION 



111 



accumulation of the peat at this place. The ordinary spruce, 

 growing upon solid ground, either frozen or unfrozen, sends its 

 roots out radially, parallel with the surface, the roots pene- 

 trating only a few inches below the surface of the ground 

 (fig. lA). The uprooted spruce tree, with its flat root base, 

 is a familiar object to all who have travelled through an Alaskan 

 spruce forest. In the White River locality, however, the roots 

 of the spruce trees, both those 

 growing at the edge of the 

 bluff, or recently overturned, 

 and those deeply buried with- 

 in the peat mass, showed quite 

 different characteristics (fig. 

 IB). Instead of a single, flat- 

 based set of radial roots, these 

 trees all show a central stem 

 often several feet long, from 

 which roots branch off at ir- 

 regular intervals, with an 

 upper set of roots near the 

 surface, corresponding to those 

 of the normal tree. An at- 

 tempt to dig out one living 

 tree for the purpose of ex- 

 amining its roots, resulted in 

 failure, for the ground was 

 found to be solidly frozen 6 



inches below the top of the Fig. 2. Section of bluff, showing glacial 

 moss, and an excavation 18 till overUin by peat and volcanic ash. 



inches deep did not reach to 



the lowest roots. Below the frost line the roots were sound 

 and undecayed, but of a darker color than the live surface 

 roots, and were apparently not functioning. 



From the above facts it seems evident that a seedling spruce, 

 having established itself on the mossy soil in this area of rap- 

 idly accumulating vegetation, sent out radial, flat-based roots 

 in a normal way, but the constantly thickening moss and fol- 

 lowing it the rising line of frozen ground cut off the food sup- 



