Genus 4. 



BIRCH FAMILY. 



611 



9. Betula glandulosa Michx. Glandular or 

 Scrub Birch. Fig. 1502. 



Betula glandulosa Michx. Fl. Bor. Am. 2: 180. 1803. 



A shrub, i°-6° high, the twigs brown, glandular- 

 warty, not pubescent. Leaves orbicular, reniform, oval 

 or obovate, glabrous, rounded at the apex, rounded, nar- 

 rowed or cuneate at the base, crenate-dentate, bright 

 green above, pale green and glandular-dotted beneath, 

 short-petioled, i'-i' long; petioles i"-z" long; staminate 

 aments commonly solitary, about i' long; pistillate 

 aments cylindric, erect, peduncled, S"-I2" long and 

 about 2" in diameter in fruit; fruiting bracts 2"-$" 

 long, the lateral lobes rather shorter than the middle 

 one; nut oblong to nearly orbicular, its wings mostly 

 narrow. 



Newfoundland to Alaska, the higher mountains of Maine 

 and northern New York, Michigan, Minnesota, in the 

 Rocky Mountains to Colorado, and to California. Also in 

 Asia. Dwarf birch. June-July. 



10. Betula Sandbergi Britton. Sandberg's 

 Birch. Fig. 1503. 



Betula Sandbergi Britton, Bull. Torr. Club 31 : 

 1904. 



166. 



A shrub or small tree, the close bark dark reddish- 

 brown, the young twigs finely pubescent. Leaves 

 oval to rhombic-ovate, acute at both ends, serrate, 

 i'-2j' long, firm in texture, dull green above, paler 

 and sparingly pubescent beneath, the slender petioles 

 about i' long; staminate aments 2'-z¥ long; fruiting 

 pistillate aments about 1' long, cylindric, slender- 

 stalked; bracts about 2" long and broad, pubescent, 

 the middle lobe obtuse or acute, longer than the 

 obtuse lateral ones; nut narrower than its wings. 



Swamps, Minnesota to Saskatchewan and Montana. 

 Spring. 



11. Betula pumila L. Low Birch. Fig. 1504. 



Betula pumila L. Mant. 124. 1767. 



A bog shrub, 2°-i5° tall, the twigs brown, be- 

 coming glabrous, the young foliage densely 

 brownish-tomentose. Leaves obovate, broadly 

 oval or orbicular, rounded at both ends or some 

 of them cuneate-narrowed at the base, rather 

 coarsely dentate, when mature glabrous and dull 

 green above, pale, persistently tomentose or 

 becoming glabrous beneath and prominently 

 reticulate-veined, i'-ii' long; petioles 1V-3" 

 long; fruiting pistillate aments oblong-cylindric, 

 erect, peduncled, 1' long or less, about 3" in 

 diameter ; bracts puberulent or ciliolate, the lateral 

 lobes spreading at right angles, shorter than the 

 middle one; nut oblong, mostly rather broader 

 than its wings. 



In bogs, Newfoundland to western Ontario and the 

 Northwest Territory, south to New Jersey, Ohio and . 

 Minnesota. Also in Europe and Asia. Dwarf birch. 

 Tag-alder. May-June. 



Betula glandulifera (Regel) Butler, differs in having leaves smooth or nearly so on both sides. 

 It grows from Michigan and western Ontario to British Columbia. 



