Perennial aquatic herbs, rooting in mud or free-floating. Roots many, long and feathery in floating plants. Leaves dimorphous; the emergent ones with often swollen, long petioles, and obovate, orbicular, spathulate or lanceolate blades; submerged leaves alternate, linear, with petioles sheathing stems, shortly stipulate. Flowers in well-developed spikes or these reduced to 1 or 2 flowers. Perianth funnel-shaped, with a somewhat curved tube and 6 subequal spreading lobes, blue or mauve. Stamens 3 + 3, upper included, lower exserted; anthers dorsifixed, oblong, opening by longitudinal slits. Ovary 3-locular; ovules many; style filiform; stigma slightly dilated, entire or very shortly lobed. Capsule spindle-shaped, covered with marcescent perianth. Seeds many, small, ovoid, finely ribbed. x= 8 (aneuploids, polyploidy).
Species 7, tropical America and Africa; 1 in sthn Afr.: Eichhornia natans (P.Beauv.) Solms, N Namibia and Botswana. * E. crassipes (Mart.) Solms (Water hyacinth), originally from South America, has become one of the world's worst pests of waterways; in South Africa it is a declared weed and prohibited as an ornamental plant.
Annual or perennial (sometimes short-lived), tufted, stoloniferous, mat-forming. Leaf blade linear, margins usually thickened; ligule a fringe of hairs. Inflorescence of spike-like main branches widely scattered or closely arranged along central axis; spikelets shortly pedicelled. Spikelet 2-5 mm long, dorsiventrally compressed, disarticulating above glumes, distinct elongated internode between and above glumes, rounded on back; glumes very unequal, slightly longer than spikelet, membranous, obtuse to acute, glabrous or long-ciliate on nerves, awnless; lower glume nerveless; upper glume 1-nerved. Floret 1, bisexual; lemma less firm to similar in texture to glumes, thinly membranous, broadly rounded, entire, acute to obtuse, 3-nerved, hairy, awned; awn minute, straight; callus pungent; palea glabrous or silky-hairy. Lodicules 2, fleshy, glabrous. Stamens 3. Ovary glabrous. Caryopsis ellipsoid.
Species 4, southern tropical Africa and Texas, United States of America; 3 in sthn Afr., mainly N Namibia and Botswana.
Annual, tufted or culm solitary. Leaf blade linear, flat or rolled; sheaths rather loose, smooth and glabrous; ligule an unfringed membrane. Inflorescence a panicle, spike-like or open, rarely a raceme; spikelets pedicelled, +/- secund. Spikelet 6-20 mm long, laterally compressed, usually disarticulating above glumes; glumes unequal, usually shorter than spikelet, dissimilar, rounded on back, awnless or awned; lower glume sometimes minute, 0-1-nerved; upper glume 1-3-nerved, acute to acuminate. Florets 2-many, bisexual, sometimes upper ones reduced to lemma; lemma tapered, 3-5-nerved, entire, awned; awn median, apical, straight, more than half as long as to longer than body of lemma; callus short, glabrous; palea 2-keeled, hyaline. Lodicules 2, unequally lobed. Stamens 1 or 2, rarely 3. Ovary glabrous or minutely hairy at apex. Caryopsis linear or ellipsoid. x= 7 (polyploidy).
Species +/- 23, temperate regions, mostly Mediterranean; 4 naturalised in sthn Afr., Mpumalanga, Free State, KwaZulu-Natal, Lesotho, Northern, Western and Eastern Cape.
Annual or perennial, tufted or decumbent, sometimes stoloniferous. Leaf blade expanded; ligule a fringed membrane to a fringe of hairs. Inflorescence of 2-many or solitary, 1-sided racemes, scattered alternately on a central axis; rachis 3-angled or flat; spikelets solitary or paired, more rarely in clusters of 3 or 4; pedicels often reduced to disc-tipped stumps; lower glume turned away from rachis (abaxial). Spikelet dorsiventrally compressed, plano-convex, ovate or lanceolate, falling entire at maturity; glumes unequal, dissimilar, awnless; lower glume usually shorter than spikelet, 3-5-nerved; upper glume as long as spikelet, 5-11-nerved. Florets 2; lower floret male or sterile; lemma 5-7-nerved, resembling upper glume, awnless; palea almost as long as lemma or reduced, 2-keeled; upper floret bisexual; lemma shorter than spikelet, firmer than glumes, indurated, entire, rounded at apex, margins inrolled and clasping only edges of palea, rugose, faintly 5-7-nerved, mucronate or awned; awn scabrid, straight, shorter than spikelet; palea obtuse, almost as long as and same texture as lemma, 2-keeled. Lodicules 2, small, cuneate. Stamens 3. Ovary glabrous; styles plumose. Caryopsis broadly ellipsoid to subrotund, dorsiventrally compressed. x= 7, 9, 15 (polyploidy).
Perennial, tufted. Leaf blade expanded or rolled; ligule a fringe of hairs. Inflorescence an open or contracted panicle or raceme; spikelets usually in triads, rarely in pairs, pedicels of triads entirely or partly fused, thus mimicking a single spikelet, rarely pedicels free, pedicels slender, often of different lengths, longest pedicel much longer than shortest pedicel. Spikelet large, 10-45 mm long, laterally to not noticeably compressed, disarticulating above glumes; glumes unequal, lanceolate, +/- persistent, chartaceous or subcoriaceous, 3-5-nerved, glabrous or hairy, hairs usually tubercle-based; upper glume usually as long as spikelet. Florets 2; lower floret male; lemma membranous, 3-7-nerved, glabrous or hairy, awnless; palea well developed; upper floret bisexual; lemma convolute, similar to firmer in texture to glumes, usually cartilaginous, 5-9-nerved, glabrous or hairy, hairs not in tufts, incised, 2-lobed, lobes awnless or awned, central awn from between lobes; awn geniculate and twisted, usually longer than body of lemma; callus conical, pungent, pubescent; palea membranous, 2-keeled, hyaline, keels thickened but not winged. Lodicules 2, cuneate, very fleshy. Stamens 3. Ovary obovoid to oblong, glabrous or apex hairy; styles plumose. Caryopsis longitudinally grooved; embryo large. x= 10, 12 (polyploidy).
Species +/- 22, tropical and sthn Afr., Madagascar, tropical America; 6 in sthn Afr., N Namibia, Botswana, northern provinces of South Africa, Swaziland, Free State, KwaZulu-Natal and Eastern Cape.
Annual or perennial, tufted, rhizomatous. Leaf blade narrow, expanded or rolled; ligule a fringed membrane or a fringe of hairs. Inflorescence an open or contracted panicle, rarely spike-like. Spikelet laterally compressed; disarticulating above glumes and between florets; glumes +/- equal or unequal, shorter than spikelet, narrowly lanceolate, 1-nerved, mostly 2-lobed, awned. Florets 3-24, bisexual; uppermost florets reduced; lemma scarious or membranous, keeled, 3-nerved, long-hairy on lateral nerves or all nerves, deeply 3-lobed, 3-awned as each lobe is awned, lateral awns shorter than central awn; awns slender, straight; callus hairy; palea shorter than lemma, hyaline. Lodicules 2, minute, delicate, glabrous. Stamens 3. Ovary glabrous; styles plumose. Caryopsis linear, trigonous. x= 10.
Species 7, Africa and Arabian Peninsula, 1 in Australia; 5 in sthn Afr., widespread.
Perennial, slender, up to 220 mm tall, densely tufted. Leaf blade narrowly linear; leaf sheaths persistent at base, sometimes becoming fibrous; ligule a narrow, fringed membrane or a fringe of hairs. Inflorescence a solitary, terminal, subsecund spike; spikelets usually appressed to rachis, alternating in 2 rows along slender triangular rachis; glumes dorsiventral to rachis. Spikelet linear-elliptic, laterally compressed, disarticulating above glumes and between florets; glumes unequal, shorter than spikelet, membranous, keeled, 1-nerved or rarely upper glume 3-nerved; lower glume often asymmetrical. Florets 5-10, all bisexual except terminal floret reduced; lemma membranous, glabrous, dorsally rounded or obtusely keeled, 1-3-nerved, rarely with 1 or 2 additional faint nerves, emarginate to 2-lobed, central nerve terminating in a mucro or slender awn, rarely laterals mucronate; callus short, villous; palea shorter than lemma, 2-keeled, keels usually winged, hyaline. Lodicules 2, truncate. Stamens 2 or 3. Ovary glabrous; styles plumose. Caryopsis narrow, subterete, obtusely trigonous in cross section. x= 10.
Species +/- 30, tropical Africa and India, Australia; 1 in sthn Afr.: Tripogon minimus (A.Rich.) Hochst. ex Steud., Namibia, Botswana, northern provinces of South Africa including Mpumalanga.