APETALOUS EXOGENOUS PLANTS. 513 



ALNUS, Tourn. Alder. 



Sterile aments elongated, drooping; Irads peltate, 

 5-bracteolate, 1-3-flowered, calyx 4-parted or scale-like; 

 stamens 4; anthers "Z-ceWtd; fertile aments short, erect; 

 bracts fleshy, 2-flowered ; calyx of four minute scales, ad- 

 herent to the bracts ; Iracts of the fruiting aments woody, 

 persistent; nut angled or winged. — Shrubs or small trees; 

 leaves petioled, serrate, the stalked buds covered with a 

 single scale ; fertile aments racemed. 



A. SERRULATA, Ait. Lcaves obovate, obtuse or abruptly 

 pointed, serrulate, commonly pubescent beneath, acute at 

 the base, short-petioled; stijniles oval, obtuse; fruiting 

 aments ovoid, short-peduncled ; fruit ovate, wingless. 

 Banks of streams. January-March. — Shrub 3°-12° high; 

 leaves 2-4' long, thickish, and partly persistent at its 

 southern limits; calyx of the sterile flozvers 4-parted. 



A. viRiDis, DC. Leaves oval, rounded at both ends, 

 slightly oblique at the base, finely and sharply serrate, 

 softly pubescent on the lower surface, or only on the veins 

 and i^etiole; stipules ovate; calyx of the sterile flowers 

 scale-like; fruiting aments ovoid, long-peduncled; /naY 

 winged. April. — A low much-branched shrub; leaves 

 l'-2' long. Mountains. 



123. WILLOW FAMILY. Order, Salicace^. 



Trees or shrubs, with soft wood, alternate simple stipu- 

 late leaves, and dioecious amentaceous /o?6'ercS destitute of 

 calyx and corolla, each solitary in the axil of a simple 

 bract; stamens 2-many; ovary 1-celled or imperfectly 

 2-celled, with numerous erect anatropous ovules in each 

 cell ; styles 2, very short, more or less united ; stigmas 

 2-lobed; friiit a 2-valved many-seeded capsule; seeds 

 minute, clothed with long silky hairs; albumen none; 

 cotyledons elliptical, flattened ; radicle pointing downward. 



22* 



