614 BETULACE^E BETULA 



1 BETULA L. Sp. 982. 



Trees or shrubs with smooth or laminated outer bark, toothed 

 simple leaves and small flowers appearing with or before the leaves. 

 Staminate aments long and drooping, solitary or in pairs, from 

 lateral or terminal leafless buds the flowers about 3 together in the 

 axil of each shield-shaped bract, consisting of a membranaceous 

 usually 4-toothed calyx and 2 stamens, subtended by 2 bractlets: 

 filament short, deeply 2- cleft, each fork bearing an anther-cell. 

 Pistillate aments oblong to cylindrical, solitary or racemose, from 

 lateral 3-5-leaved buds, the flowers 1-3 in the axil of each bract, 

 without calyx. Bracts usually 3-lobed and falling with the seed. 

 Ovary sessile: styles 2, stigmatic at the apex, mostly persistent. 

 Nuts small, lenticular, surrounded by a wing. 



B. occidentalis Hook. Fl. ii, 155. A small or middlesized tree 20-60 

 feet high and 6-18 inches in diameter, with smooth dark brown bark and 

 greenish-brown warty twigs : leaves broadly ovate to nearly orbicular, acute 

 to rounded at the apex, sharply serrate, the teeth glandular tipped, round- 

 ed or obtuse at base, phort-petioled glabrous, or sparingly pubescent on 

 one or both sides, 1-2 inches long: staminate 'aments usually 3 together at 

 the ends of slender branchlets, 2-3 inches long: pistillate aments mani- 

 festly peduricled, cylindric, spreading or pendent, 12-18 lines long, 4-6 lines 

 in diameter when mature: fruiting bracts ciliate, 2-3 lines long, their lat- 

 eral lobes ascending, usually shorter than the middle one: nutlets much 

 narrower than the wings. Along streams in the interior, Brit. Columbia 

 to California and Nebraska. As here defined perhaps includes more than 

 one species. 



B. Hallii. B. glandulosa of authors as to the Oregon plant. An erect 

 shrub 4-10 feet high, the twigs ashy-gray, glandular and somewhat pubes- 

 cent, very leafy : leaves obovate, rounded at the apex, cuneately narrowed 

 at base into short petioles, green and glabrous both sides, finely serrate, 

 10-12 lines long: pistillate aments cylindric, erect or barely spreading, 

 10-14 lines long, 2-3 lines thick, dark green, on slender peduncles 4-6 lines 

 long: fruiting bracts a line long, glabrous, the lateral lobes usually broader 

 than the middle one which is spreading and hyaline-margined : nutlets as 

 broad or broader than long, narrowly winged. Lake Labish, Marion Co. 

 Oregon: specimens collected by Mr. Gorman at Ft. Selkirk, Yukon Ter. 

 appear to be of this species. 



2 ALNUS G*ertn. Fr. & Sem. ii. 54, t, 90. (1791.) 



Shrubs or trees with alternate serrate or dentate leaves and 

 small flowers in aments. opening with or before the leaves, mak- 

 ing their first appearance during the previous season. Staminate 

 aments fascicled, drooping. Bracts shield-shaped, stipitate, in- 

 cluding the 5 bractlets and usually 3 flowers with regular 4-lobed 

 calyx. Stamens 4, inserted opposite the lobes of the calyx, with 

 very short filaments and contiguous anther-cells. Pistillate a- 

 ments panicled, short and usually erect, their bracts fleshy and 

 imbricated, including 4 bractlets and 2 flowers, connate and 

 slightly 4-lobed, in fruit woody and persistent, thickened and 

 truncate at the apex, at length divergent. Nutlets compressed, 

 mostly wingless or nearly so. 



A. Oregaiia Nutt. Sylva, i, 28, A. rubra Bong. A large tree 50-100 



