Butler : The western American birches 433 



often with a few scattered hairs; leaf-blades ^-6 cm. long, broadly 

 ovate to suborbicular, with acute apex and rounded to cuneate 

 base, sharply dentate with abruptly tipped teeth, hairy at first, be- 

 coming glabrous except along veins beneath and on basal margin, 

 veins 5 or 6 pairs; fruiting aments cylindrical, stout, 3—4 cm. long, 

 8-12 mm. thick; bractlets 4-5 mm, long, nearly as wide, the 

 middle lobe triangular, acute or obtuse, the lateral lobes obliquely 

 ovate or rhombic, acute, widely spreading, distinctly auricled at 



the base ; samara wings broader than the oval or obovate nutlet. 

 [Figure i i.] 



The bractlets resemble those of Betitla Piperi, differing in the 

 more rhombic acute lateral lobes, which are more spreading and 

 broadest at the base, the claw being much longer. The leaves 

 resemble those of B,fonttnalis but are larger, thicker and more 

 cuneate. The species occurs in the Flathead region, Montana, but 

 with this exception is not known outside of the type locality near 

 Salt Lake City, Utah. 



12. Betula. Piperi Britton, Bull. Torrey Club 31 : 165. 1904 



A tree up to 15 m. high, with slender, graceful, drooping 

 branches; bark dark brown, not separable into layers, lenticels 

 nearly white ; twigs very delicate, slender, greenish brown and 

 glandular- resiniferous, becoming nearly black; leaf-blades 5-6 

 cm. long and 4—5 cm. wide, ovate or oval, often somewhat lobed, 

 very thin, dark rich green, shining above, very pale and whitish 

 beneath, coarsely, sharply, and irregularly serrate, pubescent at 

 first, becoming glabrous, apex acute, base mostly cuneate ; fruit- 

 ing aments slender, narrowly cyhndrical, 3-5 cm. long, al^out 8 

 mm. thick; bractlets puberulent and ciliate, the lateral lobes 

 widely spreading, rounded, obliquely ovate, distinctly auricled, the 

 middle lobe triangular, acute or obtuse, the claw very short, cu- 

 neate, about equaling the lateral lobes ; samara wings usually not 

 wider than the nutlet [Figure 12,] 



The type is no. 352^ of C. V. Piper, collected near Pull- 

 man, Washington. I have found several sterile specimens along 

 the Kootenai River in northwestern Montana and also in the Flat- 

 head region. The name black birch is aptly apphed to it, this 

 color, with the very thin coarsely toothed leaves and the slender 

 fruiting aments with their characteristic auricled, short-clawed 

 .bractlets, making it very distinct. It ranges from Oregon and 

 Washington to western Montana. 



