260 FOREST TREES OF THE PACIFIC SLOPE. 



known now of its southern limit. Extends down Stikine River to Kloochman Canyon 

 (where river crosses coast range) ; occurring frequently with spruce and cottonwoods 

 northward throughout region east of coast ranges, except on Upper Pelly River above 

 Hoole River. Locally noted on Dease River, headwaters of Liard River northward to 

 Frances Lake, where timber line is about 4,000 feet ; on Stewart, Klondike, McQuestion, 

 and Yukon rivers ; at Dawson, Fort Selkirk, on Peels River, and at Fort Simpson. 

 Lewes River, but not above head of Fifty-mile River between Lake Marsh and Lake 

 Lebarge. 



Alaska. — Probably not on sea side of coast mountains, except at Lynn Canal and 

 west of it, on Kenai Peninsula and about Cook Inlet. Common in interior valleys and 

 throughout Yukon River Valley, in mountains, and toward west coast, northward as 

 far as timber extends. Noted on White and Tanana Rivers (up to 3,400 feet), Copper 

 River (below 2,000 feet), Sushitna River to headwaters, Chitna River (tributary to 

 Sushitna) and adjacent Skolai Mountains, Kuskokwim River from Kolmakof to head- 

 waters, Allen, Kanuti, Dall, and Kowak rivers (up to about 2,500 feet), Koyukuk River 

 up to Roberts Creek, and Chandler River to a few hundred feet above Chandler Lake 

 and on head tributaries to 600 feet above main river. Sea side of passes at head of 

 Lynn Canal from point a short distance below summit, becoming very common at low 

 elevations nearer sea ; locally noted at Chilkoot, Portage Bay, and on Chilkat Inlet. 

 Abundant over Kenai Peninsula plateau, reaching timberline, with white spruce and 

 balm-of-Gilead, at 1,600 to 2.000 feet elevation, and extending to shores of Turnagain 

 Arm, up Sushitna River and its tributaries and also to west side of Cook Inlet ; here 

 abundant, especially at Tyonek, reaching 2,000 to 3,000 feet elevation. Occurs sparingly 

 farther south on west shore of Cook Inlet at head of Iliamna Bay, and inland about 

 lakes Iliamna and Clark (southern limit of timber at head of Alaskan Peninsula). 



OCCURRENCE. 



In vicinity of streams and on lower hill slopes in moist gravelly soils, mingled with 

 spruces and other conifers of its range. Silvical habits, etc., undetermined. 



Mountain Birch. 

 Betula fontinalis Sargent. 



DISTINGUISHING CHARACTERISTICS. 



Mountain birch is a slender, graceful tree or tall shrub, long known as Betula 

 occidentalis Hooker, a name which is now known to belong to an entirely differ- 

 ent tree. This discovery necessitated giving the mountain birch its present 

 name, Betula fontinalis. There is still some doubt, however, in regard to the 

 true identity of at least one form of this tree. This can be cleared up only by 

 further field study. 



This tree has several conflicting and inappropriate field names, such as 

 " black birch," " sweet birch," " cherry birch," " water birch," and " canyon 

 birch." Mountain birch is proposed as mofe suitable, since the habitat of the 

 tree, in contrast with that of most other birches, is distinctly a mountainous 

 one. 



Very commonly a slender-stemmed, shrub-like tree from 10 to 15 feet high 

 (in dense thickets), but sometimes from 25 to 30 feet high and from 6 to 10 

 inches through. The deep, shiny, old-copper-colored bark of the trunks dis- 

 tinguishes it from other asociated trees. The thinly foliaged crown is composed 

 of very slender branches with delicate pendent twigs. When young the twigs 

 are greenish and more or less thickly covered with resinous, shiny dots (glands), 

 which disappear gradually in one or two seasons, during which the twigs 

 become deep red-brown or copper-brown and more and more shiny. Mature 

 leaves (fig. 114), resinous dotted at first, are smooth, except for numerous dots 

 on the lighter green under surfaces; leaf stems also with glandular specks and 

 minute hairs. Fruiting cones (fig. 114), ripe in early summer, about seven- 



