Perennial or annual herbs. Leaves mostly in a basal tuft, grass-like, linear or filiform, sheathing at the base or reduced to a sheath, sheaths open or closed. Flowers hermaphrodite or unisexual, usually very small. Perianth-segments 6, in 2 whorls, or rarely only 3, usually glumaceous. Stamens 6 or 3, free; anthers 2-celled, basifixed, opening lengthwise; pollen in tetrads. Ovary superior, 1-celled or 3-celled; styles and stigmas 1 or 3. Ovules ascending or parietal, 3 or more. Fruit a dry capsule. Seeds sometimes tailed, with a small straight embryo in the middle of endosperm.
Annual or perennial herbs, rarely shrubs. Roots fibrous. Stems erect, cylindric or rarely compressed, naked or leafy, sometimes rhizomatous or stoloniferous, and then horizontal or ascending. Leaves grass-like or cylindric, sheathing at the base, sometimes reduced to cataphylls; sheaths open and sometimes auriculate, or closed. Inflorescence terminal, often pseudo-lateral, compound or rarely simple with one flower, umbellate, paniculate, the flowers solitary or in capitula (heads); bracts leaf-like, scarious or membranous, persistent; bracteoles sometimes present. Flowers small, regular, hermaphrodite; rarely the plants dioecious. Perianth-segments 6, in two series, subequal, glumaceous, green or brown, usually membranous at the edges. Stamens 6, opposite and shorter than the perianth-segments, the 3 inner sometimes absent; filaments linear or triangular; anthers basifixed, 2-thecous, introrse, dehiscing longitudinally. Carpels 3, joined; ovary superior, 1- or 3-locular; style rarely absent; stigmas 3. Fruit a loculicidal capsule. Seeds 3 or many, ovoid to obovoid, apex sometimes apiculate, base sometimes tailed.
Notes: A comprehensive account of the synonymy can be found for most cases in Buchenau, E.P. IV, 36 (1906).
Perennial, usually rhizomatous, less often annual herbs, glabrous or with hairy leaf margins; rarely leaf abaxial surface with simple, many-celled trichomes. Silica bodies ± absent; oxalate raphides absent; stomata paracytic. Stem erect to ascending, rarely procumbent, usually terete, leafless or leaf-bearing. Leaves linear or filiform, spirally arranged, rarely distichous; sheath closed or open, often auriculate; auricles rarely joined to form a ligule-like structure; blades of basal leaves sometimes reduced (cataphylls). Inflorescence terminal, rarely pseudolateral (bract resembles a continuation of stem), compound, cymose or racemose, panicle-like or anthelate, many-flowered with flowers in many to one terminal heads or spike-like clusters; lower inflorescence bracts usually herbaceous; each branch with membranous bract and adaxial prophyll; flower bracteoles 1.2 or absent; rarely inflorescence reduced to a single terminal or lateral (subterminal) flower. Flowers small, usually up to 8 mm long (rarely to 40 mm), actinomorphic, hypogynous, usually hermaphrodite, rarely unisexual (dioecious or monoecious). Perianth segments 6, in two whorls, glumaceous, usually ± equal, free. Stamens 6 in two whorls or inner whorl reduced; filaments filiform to flattened; anthers 2-thecate, 4-sporangiate, oblong to linear, basifixed, dehiscence lateral; connective rarely with a projection; pollen in tetrads. Carpels 3, connate; ovary superior, unilocular or 3-septate to 3-locular; style 1, distally 3-branched (stigmas), papillae ±adaxial. Fruit an orbicular to oblong-ellipsoid loculicidal (rarely circum-scissile) capsule. Seeds 3.many; endosperm starchy; embryo small, broadly cylindric; outer seed-coat hyaline, whitish to brownish, loose to adpressed, sometimes forming apical and/or basal appendages; inner seed-coat usually brown to castaneous.
Most species are terrestrial or semiaquatic, occupying open grass lands or swamps. Some species of funcus are anthropochorous and weedy, some apparently restricted to eutrophic grass lands. Several species of funcus are halophytic (Snogerup 1993). The cushion-forming genera Distichia, Oxychloe, and Patosia are well adapted to harsh diurnal freezing and thawing; they are conspicuous elements of wetlands in the high Andes, sometimes reaching the altitudinallimit of the vegetation. Prionium grows in permanent streams and rivers and is important in preventing erosion during seasonal flooding.
Few important economic uses of Juncaceae are known. Many species of Juncus and Luzula are components in pastures throughout the world. Juncus effusus is used for making mats in Central America and Japan, and so is J. rigidus in the Near East. In the treeless puna of Peru, blocks of the cushions of Distichia muscoides are cut for fuel.
Vegetative propagation by means of large rhizome systems is common in many species, especially in funcus. Vegetative propagation connected with water dispersal is known in, e.g. Juncus bulbosus and J. pelocarpus. Dispersal is otherwise by seeds. The mucilaginous seeds of some species are adapted to epizoochory and their small size and ability to adhere to animals explain the wide and discontinuous distributions of many species. The fusiform seeds of some Juncus species may be anemochorous or (and) hydrochorous. Carunculate seeds of Luzula are dispersed by ants. The swelling of the testa upon moistening in some species appears to cause capsule dehiscence.
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