Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Genus Description - Fls perfect or unisexual; perianth tubular to campanulate, the tep separate or united; stamens 6, inserted on the base of the perianth; filaments slender; anthers oblong, introrse; ovules 2 in each of the 3 locules; style slender; stigmas 3, short; fr a berry with a few large rounded seeds; herbs with the lvs reduced to inconspicuous scales and replaced functionally by branches incapable of further growth and sometimes flattened and lf- like in appearance; fls small. 300, Old World.