Butler : The western American birches 



429 



brouSj mostly finely crenate leaves ; and pubescent, glandular- 

 resiniferous branchlets. The samaras are like those of Bettda 

 piiviila and B, glandulifera in being narrow-winged but the elon- 



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gated fruiting aments and finely crenate glabrous leaves at once 

 distinguish it from these species. It ranges from Oregon north- 

 ward to Alaska and Yukon Territory. 



7/Betula crenata Rydb. Ms., sp. nov. 



A shrub 2.5-4.5 m. high, with dark brown or nearly black 

 bark, branches only sparingly glandular-resiniferous, puberulent 

 or glabrous and reddish at first; leaf-blades 1-3 cm. long, 8-20 

 mm. wide, slightly pubescent at first, resinous, glabrous when 

 older, oval or elliptical, acute at both ends, crenate or crenate- 



Figure 7. Betuia cre- 

 nata Rydb. From type, 

 D. T. MacDoMgal 66^, 

 near Rost Lake, Montana. 



Figure 8. Behda Sa7id' 



bergi Britton. From B, T, 

 Butler J65, near Rost Lake 

 Montana, 



h 



serrate with very small teeth, shining dark green and reticulate- 

 veined above, with 4 or 5 pairs oi very delicate and inconspicuous 

 veins, yellowish green beneath with minute resin-dots; petioles 5-10 

 mm. long; fruiting aments 12-18 mm. long, about 6 mm, thick, 

 cylindrical ; bractlets glabrous, about 4 mm. long and 3 mm, 

 wide, middle lobe short-oblong or elliptic, obtuse or rounded at 

 the apex, lateral lobes ascending, obliquely ovate or rhombic, 

 obtuse ; samara about 2 mm. wide, wings as wide as or narrower 

 than the nutlet. [Figure 7.] 



The species is distinguished by the glabrous oval or elliptical 

 finely crenate leaves and the narrow-winged samara. It resembles 

 Betula EIrodiana in size and outline of the leaf but the coarse ser- 



