Herbs, perennial, cespitose or not, rhizomatous or stoloniferous. Culms solitary or not, terete or rounded-trigonous, usually 70+ cm. Leaves cauline; ligules absent; blades flat to involute. Inflorescences terminal or some lateral, corymbose or subcapitate, conspicuously branched; spikelets 100-1000+; involucral bracts 3-4+, spreading, leaflike. Spikelets: scales 5-6, spirally arranged, proximal 1-3 scales empty, distal 3-4 scales each subtending flower. Flowers bisexual or staminate; perianth absent; stamens 2-3; styles linear, 3-fid, base persistent, somewhat thickened. Achenes terete. x = 20. Cladium is here accepted in the strict sense, i.e., consisting of four species: C. mariscus, of the Old World, and three species treated below. The genus had been treated in a broader sense, including Machaerina Vahl (G. Kükenthal 1942). Later studies (cited by G. C. Tucker 1987) argue against such a broad circumscription of the genus. Machaerina was excluded by M. T. Strong (1997). Species of Cladium consistently differ from those of Machaerina in their smaller, less differentiated embryos and anisobilateral leaves with inverted bundles (illustrated by C. R. Metcalfe). According to G. Kükenthal (1942), Cladium mariscus comprised three subspecies: C. mariscus subsp. mariscus of Europe and Asia; C. mariscus subsp. jamaicense (Crantz) Kükenthal of the Western Hemisphere, Africa, and Hawaii; and C. mariscus subsp. intermedium Kükenthal of Australia. He synonymized C. californicum under C. mariscus subsp. jamaicense. Most American authors have treated C. jamaicense as distinct from the Eastern Hemisphere C. mariscus, a view followed here with some trepidation. Resolution of this taxonomic problem is well beyond the scope of this flora. The culms and leaves of Cladium mariscus are gathered and used in the manufacture of paper products in the Danube Delta, Romania.
Scales spirally imbricate, deep brown, forming a lanceolate to ovoid spikelet; perianth none; uppermost fl of each spikelet perfect, with 2 stamens, a terete ovary, and 2-3 stigmas; middle fls staminate or abortive; lowest scale of each spikelet empty; achene ovoid, terete, dull, pointed but not tuberculate; infl compound, cymosely branched, bearing spikelets in small terminal capitate clusters. 50+, widespread.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.