BIRCH FAMILY 



511 



2. BETULA [Tourn.] L. Sp. PI. 982. 1753. 



Trees or sometimes shrubs with close-grained hard wood, smooth aromatic resinous bark, 

 marked by long longitudinal lenticcls, often separating into thin papery sheets. Leaves 

 deciduous, simple, toothed, petioled ; stipules scarious, caducous. Aments elongated and 

 solitary or the staminate sometimes clustered, blooming in early spring before the leaves. 

 Flowers 3 in the axil of the bract, the two lateral subtended by bractlets adnate to the base 

 of the bract. Calyx in the staminate flowers 2-4-lobed, wanting in the pistillate. Stamens 2, 

 2-branched above, each branch bearing a pollen sac. Ovary sessile, compressed. Bracts 

 accrescent, 3-lobed, deciduous with the nutlet in fruit. Nutlet minute, oval or obovate, com- 

 pressed and scariously winged. [The ancient name.] 



About 30 species inhabiting the subarctic and the cooler parts of the north temperate regions. Type 

 species, Bctula alba L. 



Low shrubs; leaves usually less than 25 mm. wide, simply serrate or crenate, distinctly reticulate; wings 

 much narrower than the nutlets. 



Twigs not pubescent, thickly resinous glandular; leaves mostly rounded. 1. B. glandulosa. 



Twigs pubescent or hairj'; leaves obovate-cuneate. 2. B. pitnida glandulifera. 



Trees or large shrubs; leaves usually over 25 nun. long, indistinctly reticulate and usually more or less 

 doubly serrate; wings usually broader than the nutlet. 



Bark separable into thin layers. 3. B. papyrifera occidentalis. 



Bark not separable into thin layers, reddish or yellowish brown. 4. B. foniinalis. 



1. Betula glandulosa Michx. Glandular or Scrub Birch. 



Fig. 



1241. 



Bctula glandulosa W\chyi. Y\. Tior. Am. 2: 180. 1803. 



Shrub 3-12 dm. high, the twigs densely dotted with 

 wart-like resinous glands, otherwise glabrous. Leaves 

 broadly obovate to orbicular, 12-25 mm. long, rounded 

 at apex, usually cuneate at base, crenate-dentate, reticu- 

 lated, pale green and glandular-dotted beneath, firm 

 and subcoriaceous ; petioles 4-6 mm. long ; fruiting 

 aments 12-25 mm. long, 3-4 mm. thick, mostly erect, 

 sessile or short-stalked; bractlets with divergent lobes 

 rounded at the apex ; nutlets with a narrow or obscure 

 wing. 



Usually in sphagnum bogs, Canadian Zone; Arctic regions 

 of North America and Asia, south to Oregon, Colorado and 

 New York. Type locality: about lakes, from Hudson Bay 

 to Lake Mistassini. 



2. Betula pumila glandulifera Kegel. Western Low Birch. 



Fig. 



1242. 



Betula pumila glandulifera Regel, B'ull. Soc. Nat. 



Moscou 382 : 410. 1866. 

 Betula hallii Howell, Fl. N. VV. Am. 1 : 614. 1902. 

 Betula glandulifera Butler, Bull. Torrey Club 36: 425. 



1909. 



Shrub, 1-2 m. high, the slender reddish 

 brown branchlets slightly resiniferous or glan- 

 dular-dotted, clothed with long scattered hairs. 

 Leaves 2-4 cm. long, 15-30 mm. wide, obovate 

 to nearly orbicular, acute or ol)tuse at apex, 

 cuneate at base, serrate to crenate-serrate, dark 

 green and shining above, resinous beneath, 

 hairy on the veins when young; fruiting 

 aments 15-20 mm. long, 3-5 mm. thick, erect; 

 bractlets puberulent, middle lobe truncate, 

 longer than the ascending rounded lateral 

 ones ; wings much narrower than the oval 

 body. 



In bogs, especially sphagnum bogs, Humid Transi- 

 tion and Canadian Zones; Alaska to Marion County, 

 Oregon, east to Minnesota. Type locality: not in- 

 dicated. 



