512 

 3. 



BETULACEAE 



Betula papyrifera occidentalis (Hook) Sarg. Western Paper Birch. 



Fig. 



1243. 



Betula occidentalis Hook. Fl. B'or. Am. 2: 155. 

 1839. 



Betula papvracea occidentalis Dippel, Hanb. Laub- 

 holzk. 2: 177. 1892. 



Betula microphylla occidentalis M. E. Jones, Contr. 

 West. Bot. "12: 77. 1908. 



Betula papyrifera occidentalis Sarg. Journ. Ar- 

 nold Art. 1: 63. 1919. 



A large tree attaining a maximum height 

 of 40 m. with a trunk diameter of 10-13 

 dm. Bark orange-brown or white, shining, 

 peeling off readily; the inner bark bright 

 orange-yellow ; young twigs loosely covered 

 with long hairs, glandular. Leaves 6-10 cm. 

 long, ovate, acute or acuminate at apex, 

 subcordate to subcuneate at base, doubly 

 serrate with irregular long-pointed teeth, 

 glabrous with age except for a tuft of hairs 

 in the axils of the veins ; petioles about 15 

 mm. long; fruiting aments cylindric, spread- 

 ing, 3-4 cm. long, 10-12 mm. thick; bract- 

 lets ciliate, 5-6 mm. long, middle lobe 

 elongated, awl-shaped, the lateral lobes 

 ovate or rhombic, widely spreading; wings 

 but little wider than the nutlet. 



Low ground bordering streams and lakes, Transition Zone; southwestern British Columbia and north- 

 western Washington to eastern Washington, northern Idaho, and northern Montana, west of the continental 

 divide. Best developed along the Fraser River, B'ritish Columbia, and on the islands of Puget Sound. 

 This and its eastern relative, the typical Betula papyrifera, have been considered by some botanists as varie- 

 ties of the Old World Betula alba. Type locality: "Straits of Juan de Fuca." 



Betula papyrifera subcordata (Rydb.) Sarg. Journ. Arnold Arb. 1: 63. 1919. (.Betula subcordata 

 Rydb. Bull. Torrey Club 36: 436. 1909.) A small tree, 8-15 m. high with a trunk 3-5 dm. in diameter. 

 Bark white or sometimes orange-brown, separating freely into thin layers. Leaves broadly ovate, 5-7 cm. 

 long, acute or short-acuminate at apex, rounded or subcordate at base, finely and often doubly serrate, 

 glabrous; fruiting aments drooping on slender peduncles, cylindric, 25-35 mm. long, 8 mm. thick; bractlets 

 puberulous, ciliate on the margins, the middle lobe acute, longer than the broad truncate lateral lobes; wings 

 broader than the body of the seed. 



Stream banks. Transition and Canadian Zones; British Columbia and western Washington to Alberta, 

 northern Montana, Idaho, and northeastern Oregon (Minum River Valley). Type locality: Hatwai Creek, 

 Nez Perce County, Idaho. 



4. Betula fontinalis Sarg. Spring Birch. 



Fig. 1244. 



Betula fontinalis Sarg. Bot. Gaz. 31: 239. 1901. 

 Be*i(/a /'i>eri Britton, Bull. Torrey Club 31: 165. 1904. 

 Betula viicrophvlla fontinalis M. E. Jones, Contr. West. Bot. 



12: 77. 1908. 

 Betula occidentalis, f. inopina Jepson, Fl. Calif. 1 : 349. 1909. 



A shrul) or sometimes a small tree 10 m. high, 

 with a trunk 1-4 dm. in diameter. Bark dark bronze 

 and shining, not separable into layers; young twigs 

 roughened "by large resinous glands. Leaves broadly 

 ovate, 3-5 cm. long, acute at apex, cuneate to sub- 

 cordate at base, sharply and often doubly serrate, 

 resinous glandular on the upper surface when young, 

 becoming dull dark green above, paler and shmmg 

 beneath and covered with minute glandular dots; 

 fruiting aments 25-30 mm. long, spreading or pendu- 

 lous on slender grandular peduncles; bractlets 

 glabrous or puberulent, ciliate on the margins, lateral 

 lobes erect, much shorter than the middle one; wing 

 wider than the nutlet. 



Along mountain streams, Canadian Zone; eastern B'ritish 

 Columbia to South Dakota, south to New Mexico and Inyo 

 County, California. The California specimens have the wings 

 equalling or narrower than the nutlet. Type locality: Sweet- 

 water River, Wyoming. 



