Fimbristylis dichotoma (L.) Vahl

  • Authority

    Acevedo-Rodríguez, Pedro & collaborators. 1996. Flora of St. John, U.S. Virgin Islands. Mem. New York Bot. Gard. 78: 1-581.

  • Family

    Cyperaceae

  • Scientific Name

    Fimbristylis dichotoma (L.) Vahl

  • Description

    Species Description - Tufted perennial to 80 cm tall; rhizome short, nodose; culms obscurely angled, nearly cylindrical near base, compressed above 0.8-2 mm wide near base, many-ribbed, green, glabrous. Leaves 5-7(-10); blades flat to somewhat inrolled, to 40 cm long, 1.5-3 mm wide, many-veined, green, glaucous, glabrous, rarely remotely pilose, with ciliate-scabrous margins, the apex with a curved tip; sheaths finely veined, glabrous or sometimes sparsely pilose, light reddish brown, ligulate, with a horizontal band of appressed hairs at ventral base of blade, ca. 0.5 mm wide, the inner band pilose above, ciliate along margins. Inflorescence a dense, simple to compound cyme, 2-10 cm diam.; involucral bracts 5-6, scabrous on margins, with sheathing base usually ciliate and pubescent, the lower ones leaflike, to 10 cm long, 1-2 mm wide, usually equaling to overtopping the inflorescence, the upper ones linear to filiform; rays flattened to subcompressed, remotely scabrous on margins, glabrous, the primary rays to 6 cm long, 0.2-1 mm wide, secondary rays shorter. Spikelets 10-60, ovate to ovate-lanceolate or oblong-lanceolate, acute, 4-8(-15) x 2-3.5 mm , solitary at ray tips, sometimes fasciculate. Scales ovate to broadly ovate or oblong-ovate, 2.1-3 x 1.8-2.2 mm, 3-nerved, glabrous, shiny, pale brown to reddish brown, usually dark brown toward apex, midrib pale green, the apex acute to obtuse, mucronate. Stamens 1 or 2, the anthers linear, 0.9-1 mm long, apiculate at apex; styles 2-branched, the branches one-third to one-half the length of the style, the unbranched portion flattened, ca. 0.5 mm wide, fimbriate along margins. Achene 2-sided, obovate, 1-1.3 x 0.8-1 mm , rounded and apiculate at apex, shortstipitate at base, whitish to brownish, coarsely striate-reticulate with (5-)7-9(-12) rows of horizontally arranged, rectangular cells on each side, the longitudinal ribs between the cells prominent.

  • Discussion

    Scirpus diphyllus Retz., Observ. Bot. 5: 15. 1789. Fimbristylis diphylla (Retz.) Vahl, Enum. PL 2: 289. 1805.

    Fimbristylis laxum Vahl, Enum. PL 2: 292. 1805.

    Fimbristylis annua (All.) Roem. & Schult. var. diphylla (Retz.) Kiik., Repert. Spec. Nov. Regni Veg. 23: 196. 1926.

  • Distribution

    Occasional in wet areas along roadsides. Bordeaux (B537, A3831), Bethany (B277). Also on St. Croix, St. Thomas, Tortola, and Virgin Gorda; cosmopolitan, primarily in warm-temperate and tropical regions.

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