Plants annual or perennial; usually cespitose, sometimes rhizomatous, rarely stoloniferous. Culms 10-250 cm, usually erect, rarely prostrate, glabrous. Sheaths open, usually glabrous, often ciliate at the apices; ligules of hairs; blades flat, folded, involute, sometimes terete. Inflorescences terminal, open or contracted panicles, sometimes partially included in the uppermost sheath. Spikelets rounded to laterally compressed, with 1(-3) floret(s) per spikelet; disarticulation above the glumes. Glumes 0-1-veined; calluses poorly developed, usually glabrous; lemmas membranous or chartaceous, 1(3)-veined, unawned; paleas glabrous, 2-veined, often splitting between the veins at maturity; anthers (2)3. Fruits utricles or achenes, ellipsoid, obovoid, fusiform, or quadrangular, pericarp free from the seed, becoming mucilaginous when moist in most species, remaining dry and partially adherent to the seed in S. heterolepis and S. clandestinus. Cleistogamous spikelets occasionally present in the lower leaf sheaths. x = 9. Name from the Greek sporos, seed, and bolos, a throw, referring to the free seeds, which are sometimes forcibly ejected when the mucilaginous pericarp dries.
Plants perennial; synoecious; rhizomatous, rhizomes short or elongate. Culms 50-250 cm, solitary or few. Leaves cauline; sheaths open; ligules of hairs, dense, short; blades elongate, long tapering. Inflorescences terminal, simple panicles, usually exserted and exceeding the upper leaves, open to contracted; panicles 8-80 cm long, to 60 cm wide, simple, flexible, branches not spikelike, not disarticulating. Spikelets with 1 floret, laterally compressed, unawned; rachillas not prolonged; disarticulation above the glumes, achenes falling with the lemmas and paleas. Glumes subequal to unequal, 1-veined, acute; calluses evidently hairy, hairs 1/4-7/8 as long as the lemmas; lemmas similar to the glumes, from shorter than to longer than the upper glumes, 1-veined, acute, unawned; paleas longitudinally grooved; anthers 3, 2.4-5.5 mm; ovaries glabrous. Fruit an achene, pericarp free from the seed. x = 10. Name from the Greek kalamos, reed, and Vilfa, a genus of grasses.
Spikelets 1-fld, articulated above the glumes; glumes lanceolate to ovate, 1-veined, from much shorter to somewhat longer than the lemma; lemma membranous or herbaceous, rounded on the back, veinless or 1(3)-veined, obtuse to acuminate, awnless; palea about as long as the lemma or longer, of similar texture, usually conspicuous and in some spp. wider than the lemma; grain in most spp. soon separating from the lemma and palea, falling free; pericarp free from the seed; annual or perennial grasses with narrow, often involute lvs, minute or no ligule, and open or contracted panicles of rather small spikelets. 100, mostly of warm reg., esp. in the New World.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Spikelets 1-fld, articulated above the glumes; glumes chartaceous, 1-veined, the outer ovate, the inner much longer, lance-ovate; lemma chartaceous, obscurely 1-veined, acute, awnless, the callus bearded; palea about as long as the lemma; rachilla not prolonged; rhizomatous perennials with overlapping basal sheaths and long, narrow, usually involute blades; ligule a dense fringe of short hairs; infl an open or contracted, ovoid to oblong panicle.
4, N. Amer.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.