102 FISHERY AND FUR INDUSTRIES OF ALASKA IN 1912. 



scattered the lichen, "reindeer moss," is the predominating feature, 

 but considerable meadows of grass occur. Dwarf willows are found 

 extensively in the ravines and protected coves far above timber line. 

 Scrub alders also often form dense thickets above timber line and 

 occur sometimes as a fringe above the white spruce and birch forest 

 where this reaches the tree line. In many places dwarf birch and 

 blueberries are found abundantly in large patches a short distance 

 above the limit of trees. 



The larger rivers form in various portions extensive mud or sand 

 bars which at first become covered with equisetum. A few years 

 later wiUows appear and they in turn give way to alders. Finally 

 cottonwoods succeed the willows and alders only to be crowded out 

 by the white birch and white spruce forest. If sufficient time be 

 given the formation the white spruce finally becomes the dominant 

 tree. In the shade of the stream forests a few grasses grow in places, 

 and if the shade is not too heavy, bushes of cranberry, raspberry, or 

 currant may cover the ground. Dwarf alders may also persist, but 

 outside of these there are few other shrubs. 



On the south hiU slopes bordering Lake Minchumina an extensive 

 white-birch forest is found. The trees of this forest are very uniform 

 in size and height, being from 6 to 12 inches m diameter and about 

 50 feet in height, with no large branches till near the top. A few red 

 birches and young white spruce are also found. The forest floor is 

 covered with low cranberry bushes, other shrubs being nearly absent. 

 No pure birch forest of this extent was seen elsewhere. 



In the change from a lake to a swamp and finally to land trees do 

 not gain a foothold until several other stages have been passed 

 through. Around a typical lake of the interior there is, first, a 

 fringe of equisetum extending into the water untU it has reached a 

 depth of about a foot; next comes a fringe of sedges which may start 

 at the very edge of the water; then, in order, on the drained ground 

 comes a strip of grass and finally wiUows, alders, cottonwoods, and 

 the forest of white spruce and white birch. Within the lake itself 

 there are large patches of water lilies. In the black-spruce forest there 

 is another form of lake border in which sphagnum moss grows directly 

 to the water's edge and there is little or no grass, sedge, or equisetum 

 about the lake. 



In the level parts of the valleys and on some of the high plateaus 

 extensive formations of niggerheads occur. The niggerheads are 

 formed by the growth of thick, tough clumps of grasses, which elon- 

 gate each year until the head is several feet above the ground. As 

 the tops grow very close together it is almost impossible to travel 

 through a country composed of high niggerheads. These grasses are 

 often found in black-spruce formations with the spaces between the 

 heads filled with moss. As the niggerhead formation often changes 



