Monographs Details: Alnus
Authority: Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Description:Genus Description - Staminate catkins pendulous, usually clustered, each bract subtending 3 fls with minute, 4-parted cal and 4 stamens with short, undivided filaments; pistillate catkins becoming woody, long-persistent, short, ovoid to ellipsoid or short-cylindric, each bract subtending 2 fls without cal; bracts of the pistillate catkins adnate to the bractlets, the compound unit cuneate, rounded or truncate and lobed at the summit; fr a small achene or samara, crowned with the 2 short, persistent styles and surrounded by a thin margin or membranous wing; trees or shrubs with 3-angled pith and broad, ovate to obovate, deciduous lvs. 30, mostly N. Hemisphere.