Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Genus Description - Spikelets several to many in simple or compound, often umbelliform cymes or glomerules, forming a terminal infl subtended by a cluster of sheathless, leafy or scarious invol bracts; scales spirally imbricate; fls perfect; perianth none; stamens 1–3; style 2–3-cleft, wholly deciduous, usually enlarged at base, the unbranched part often flattened and fimbriate especially distally; radicle lateral; herbs with a few long, grass-like lvs near the base, the sheath entire or short-ciliate. 200, warm reg. Spp. 3–5 are closely related and might with some reason be treated as well marked vars. of the tropical F. spadicea (L.) Vahl.