80 BETULACE^E. Betula. 



2. B. glandulosa, Michx. A low bush, 4 to 6 feet high or less, the dark-col- 

 ored branches usually more or less resinous-glandular : leaves small (a half to an inch 

 long), obovate to oblong-obovate, mostly cuneate at base, rounded and crenate above, 

 on slender petioles 1 to 3 lines long, smooth and often resinous-coated : fruiting 

 aments 3 to 1 2 lines long ; the deeply 3-lobed bracts slightly ciliate : seed orbicular- 

 winged. Flora, ii. 180; Eegel, DC. Prodr. xvi 2 . 172; Gray, Manual, 460. 



Plumas County (Mrs. R. M. Austin) ; Oregon (Hall) ; northward to Sitka and east through 

 British America to the Atlantic, in the Rocky Mountains, and in the colder portions of the North- 

 ern States. 



2. ALNUS, Tourn. ALDER. 



Bracts of staminate aments shield-shaped and stipitate, including 5 bractlets and 

 usually 3 flowers ; perianth regular, 4-lobed. Stamens 4, opposite the lobes, with 

 very short filaments and contiguous anther-cells. Bracts of pistillate aments fleshy 

 and imbricate, including 4 bractlets and 2 flowers, cuneate and slightly 4-lobed, in 

 fruit persistent and woody, thickened and truncate above, at length divergent. 

 Nutlets compressed, mostly wingless or nearly so. Shrubs or small trees, in moist 

 places, with smooth bark, the flowers preceding or appearing with the leaves ; 

 aments terminating leafless branchlets or peduncles, the staminate long and droop- 

 ing, the pistillate ovoid or oblong, erect. 



A genus of about 15 species, half of them American. The timber is almost imperishable in 

 water, the wood is valuable in cabinet work, .the bark is used for tanning and dyeing, and 

 the charcoal is usually employed in the manufacture of gunpowder. The Californian species 

 belong to section Gymnothyrsus, Spach, the flowers preceding the leaves, and the racemed aments 

 formed the previous year. 



* Fruit surrounded by a narrow somewhat membranous wing. 



1 . A. rubra, Bongard. Branches rather stout, dark brown dotted with white : 

 leaves thick, rusty-pubescent beneath, glabrate above, ovate to elliptic, 2 to 6 

 (sometimes 8) inches long, acute, rounded or more or less cuneate at base, coarsely 

 and rather obtusely toothed, the teeth crenate and margin narrowly revolute : fruit- 

 ing aments roundish ovate to oblong, a half inch or sometimes an inch long, the 

 bracts much thickened above : nutlets 1^ lines long, nearly orbicular or obovate. 



-Veg. Sitch. 162; Regel, DC. Prodr. xvi 2 . 186. A. Oreyana, Nutt. Sylva, i. 28, 

 t. 9. A. incana, var. rubra, Regel, Monogr. 99, t. 17, tig. 3, 4. 



From Sitka to San Francisco ; frequent on the Oakland Hills. Described by Nuttall as be- 

 coming 30 or 40 feet high, and Bolander speaks of it as a large tree. 



* * Fruit more or less acutely margined, not winged. 



2. A. rhombifolia, Nutt. Branches more slender, dark brown, scarcely dotted : 

 leaves slightly pubescent beneath, smoothish above, ovate (or obovate) to ovate- 

 oblong, 2 or 3 inches long, rounded at the summit or acute, cuneate at base, irregu- 

 larly glandular-denticulate : fruiting aments oblong, 6 to 8 lines long, the bracts 

 rather thin above : nutlets a line long, very broadly obovate, with a thickened 

 margin. Sylva, i. 33. A. glutinosa, var. serrulata, Regel, Monogr. 106, in part. 

 A. serrulata, var. rugosa, Regel, DC. Prodr. xvi 2 . 188, in part. 



From Oregon (Hall) to Southern California; at San Felipe (Palmer), known as "White 

 Alder." "The common California alder, 20 to 30 feet high and 2 or 3 feet in diameter," ac- 

 cording to Bolander ; 30 to 50 feet high, Peckham. Bark light ash-gray. 



3. A. oblongifolia, Torrey. Branches light brown, sparingly dotted : leaves 

 thick, slightly pubescent or glabrous beneath, smooth above, oblong-lanceolate, 2 to 

 6 inches long, acute or acuminate, cuneate at base, serrate, the teeth with scattered 

 glandular deiiticulations : staminate aments stout, 2 to 4 inches long : fruiting 



