194 TREES OF NORTH AMERICA 



die; pistillate aments about \' long, with ovate-lanceolate light yellow-green puber- 

 ulous scales ciliate on the margins. Fruit: nuts \' long, gradually narrowed at the 



apex, their involucres 1' long, nearly glabrous at the apex, sometimes slightly stained 

 with red toward the base, in clusters I'-l^' long and about |' broad, on stems ^' long. 



A tree 20-30 high, with a trunk 12'-18' in diameter, usually divided 1 or 2 

 above the ground into 3 or 4 stout upright stems 4'-5' thick, slender pendulous often 

 much contorted branches forming a narrow round-topped symmetrical head, and 

 slender branchlets dark green and coated with hoary tomentum when they appear, 

 dark red-brown and pubescent during their first summer, becoming light cinnamon- 

 brown, glabrous, and lustrous in the winter, and ultimately ashy gray. Winter- 

 buds ovate, dark red-brown, about -|' long. Bark internally bright orange color, 

 I' thick, separating into loose hanging plate-like scales light gray slightly tinged 

 with red, l'-2' long and 1' or 2' wide. Wood light reddish brown, with thin sap- 

 wood. 



Distribution. Only on the southern slope of the canon of the Colorado River in 

 Arizona at elevations of 6000-7000 above the sea near Talfrey, seventy miles 

 north of Flagstaff. 



3. BETULA, L. Birch. 



Trees, with smooth resinous bark marked by long longitudinal lenticels, often sep- 

 arating freely into thin papery plates, becoming thick, deeply furrowed, and scaly at 

 the base of old trunks, short slender branches more or less erect and forming on young 

 trees a narrow symmetrical pyramidal head, becoming horizontal and often pendu- 

 lous on older trees, tough branchlets, short stout spur-like 2-leaved lateral branchlets 

 much roughened by the crowded leaf-scars of many years, and elongated winter- 

 buds covered by numerous ovate acute scales, and fully grown and bright green at 

 midsummer. Leaves open and convex in the bud, often incisely lobed; stipules ovate 

 and acute or oblong-obovate, scarious. Flowers in 3-flowered cymes, the lateral 

 flowers of the cyme subtended by bractlets adnate to the base of the scale of the 

 ament; staminate aments long, pendulous, solitary or clustered, appearing in summer 

 or> autumn in the axils of the last leaves of a branchlet of the year or near the ends 

 of the short lateral branchlets, erect and naked during the winter, their scales in the 

 spring broadly ovate, rounded, short-stalked, yellow or orange-color below the middle 



