BIRCH FAMILY 



513 



3. ALNUS [Tourn.] Hill, Brit. Herb. 510. 1765. 



Trees and shrubs with astringent scaly bark, soft close-grained wood, naked leaf buds and 

 deciduous dentate or serrate, petioled leaves. Flowers monoecious, both kinds in ainents ; 

 the staminate aments clustered at the ends of the branchlcts, long and pendulous, the pistillate 

 clustered usually near the base of the staminate cluster, erect. Staminate f.owers 3-6 in each 

 axil, consisting of a 4-parted perianth and 1-4 stamens, subtended by 2-4 bractlets. Pistillate 

 flowers 2 in the axils, without perianth, subtended by 2-4- bractlets, adnate to the scales and 

 becoming woody in fruit, forming an ovoid or subglobose cone. Nutlet flat, ovate or oblong, 

 with lateral wings or membranous border. [The ancient Latin name.] 



About IS species inhabiting the northern hemisphere and the Andes of South America. Type species, 

 Ahiiis vulgaris Hill. 



Flowers developed with the leaves on the twigs of the season; fruiting peduncles slender, longer than the 



cones; leaves shining; nutlets with a broad membranous wing. 1. A. siiiiiata. 



Flowers developed on last year's twigs, opening before the leaves in early spring or winter; fruiting pedun- 

 cles shorter than the cones; leaves dull. 

 Leaves rusty pubescent beneath at least on the veins, revolute on the margins; stamens 4; nutlets with a 



narrow somewhat membranous wing. 2. A. oregona. 



I-eaves green beneath not revolute on the margins; nutlets merely margined. 



Leaves mostly cuneate at base, doubly serrate, not lobed except on vigorous shoots; stamens 2 or 3. 



3. A. rlwiiibifolia. 

 Leaves rounded or cordate at base, doubly serrate and lobed; stamens 4. 4. A. tenuifolia. 



1. Alnus sinuata ( Regel) Rydb. Wavy-leaved or Sitka Alder. Fig. 1245. 



Alniis viridis sinuata Regel, in DC. Prod. 26: 



183. 1868. 

 Alnus sinuata Rydb. Bull. Torrey Club 24: 



190. 1897. 



Alnus sitchensis Sarg. Silva N. Am. 14: 61. 

 1902. 



A small tree attaining a maximum 

 height of 15 m. and a trunk diameter of 

 20 cm., or more often a shrub forming 

 thickets. Leaves ovate, 7-15 cm. long, 

 acute at the apex, rounded or cuneate at 

 base, shallowly lobed and doubly glandu- 

 lar-serrate, yellow-green above, pale and 

 shining beneath, glabrous or long-hairy 

 on the tnid-rib and axils of the veins ; 

 petioles 12-18 mm. long; staminate 

 aments with ovate apiculate scales ; cones 

 12-15 mm. long, their scales truncate 

 and thickened at apex ; nutlet oval, 

 about as wide as the wings. 



Alpine streams, Canadian and Hudsonian 

 Zones; Alaska to Oregon and Colorado, also 

 Siberia. Type locality: Kamchatka. 





4. 



-^1*" 



2. Alnus oregona Nutt. Oregon or 

 Red x\Ider. Fig. 1246. 



Alnus rubra Bong. Mem. Acad. St. Petersb. \'I. 2: 



162. 1837, not Marsh. 1785. 

 Alnus oregona Nutt. Sylva 1 : 28. 1842. 



Tree 15-25 m. high, with a trunk 6-12 dm. 

 in diameter ; bark thin, pale gray or nearly 

 white, the inner red-brown. Leaves ovate 

 7-12 cm. long, acute at apex, cuneate at base, 

 crenately lobed and minutely glandular-den- 

 tate, tomentose when young, becoming dark 

 green and glabrous or sparsely pubescent on 

 the upper surface, rust) pubescent on the 

 lower; petioles 15-20 mm. long; staminate 

 aments 10-15 cm. long, their scales ovate, 

 acute, glabrous ; cone ovate to oblong, 20-25 

 mm. long; scales truncate, much thickened 

 toward the apex; nutlet ovate, much broader 

 than the membranous wing. 



Stream banks, Humid Transition and Canadian 

 Zones: southern Alaska south in the coastal region 

 to Santa Barbara County, California. Type locality: 

 probably western Oregon. 



