424 



Butler: The western American birches 



Leaves obovate, apex rounded, base cuneate ; twigs 

 pubescent, not or slightly glandular; fruiting 

 anient 3-4 cm, long, slender, 6. B, Hallii. 



Leaves coarsely serrate. 



Leaves obovate, apex acute or obtuse, base cuneate ; 

 twigs glandular-resiniferous, with long coarse 

 scattered hairs ; fruiting ament I-2 cm. long. 2. B, glandtdifera^ 



I. Betula glandulosa Michx. Fl. Bor,-Am. 2 : i8o. 



1803 



gray, densely 



A low shrub 1-2 m. high or procumbent at high elevations ; 

 twigs and branchlets coarse, reddish brown to 

 glandular-resiniferous but not hairy or pubescent ; leaf-blades 

 1-2.5 ^"^^ lo^gi broadly obovate to orbicular, often wider than 

 long, with rounded apex and mostly cuneate base, finely crenate 

 or crenate-serrate, reticulated, with the veins often impressed above, 

 glabrous, often thickly dotted with minute resinous glands; petioles 

 reddish, 2-10 mm. long; fruiting aments i- 

 thick, cylindrical ; bractlet 4-6 mm, long, finely ciliate and puber- 

 ulent, about equally 3-lobed, lateral lobes ascending, rounded, 

 nearly as long as the rounded middle lobe ; samara nearly orbic- 

 ular, about 2 mm. broad, the wings very narrow. [Figure i.] 



This species is readily distinguished by its densely glandular- 

 resiniferous twigs and branchlets and the small rounded crenate 



2 cm. long, 4-5 mm. 



Figure i. Behda glandulosa 



Michx. From F. E, 6- E, S. 



CUmenfs J/ J, Rnxton Park, Colo- 

 rado. 



FiGURK 2. Betula glandulifera 

 (Kegel) Butler. From ^, T, But- 

 ler^o^^ Rost Lake, Montana. 



or crenate-serrate leaves. It ranges from California to Alaska 

 and eastward throughout the Rocky Mountains, across the con- 

 tinent to the north. The eastern forms differ slightly from those 

 of the west. 



