Eleocharis geniculata (L.) Roem. & Schult.

The name Eleocharis caribaea (Rottbøll) S. F. Blake is considered by most contemporary authorities to be misapplied (K. L. Wilson 1990). Eleocharis geniculata has been reported from South Carolina; I have not seen a voucher.

Plants tufted, without creeping rhizomes. Culms to 45 cm × 0.2–1 mm. Leaves: distal leaf sheaths persistent, firm, distally tightly sheathing, apex acute. Spikelets orbicular to ovoid, 1–9 × 1–4 mm, apex rounded to acute; proximal scale without flower, not amplexicaulous; floral scales to 125, 11–14 per mm of rachilla, tightly appressed, dark red-brown to stramineous, ovate to elliptic, 0.8–3 × 0.6–2(–2.3) mm, membranous to cartilaginous, apex rounded to acute. Flowers: perianth bristles (0–)4–8, typically 7, red-brown, rarely whitish, vestigial to much exceeding tubercle, typically equaling achene, spinules few to dense; styles 2-fid. Achenes brown ripening to black, biconvex, orbicular to obpyriform, 0.5–1.1 × 0.3–0.7 mm, apex rarely constricted proximal to tubercle, very finely reticulate at 40X. Tubercles stramineous to whitish, umbonate to subconic, 0.2–0.4 × 0.2–0.5 mm, apex rounded to acute. 2n = 10.

Tufted annual, 12-25 cm. Roots white, fibrous. Stem 0.5-1 mm diam., green, with 5-6 obtuse angles separated by deep grooves. Open sheaths c. 5 mm, wide, scarious; lower closed sheath to 15 mm, reddish brown or green, mouth oblique, upper to 50 mm, green or basal parts reddish, with 5 nerves, mouth oblique, margin narrowly scarious; blades 0 or minute tip. Spike 3-6 x 3-4 mm, ovoid or globular, with 50 or more very closely imbricating glumes; basal glume fertile, not distinct from other glumes or its mid-nerve more pronounced and stronger; glumes 1.7-2.2 mm, not in protruding spiral rows, cymbiform, rounded, mid-nerve not very distinct, not reaching apex, sides grey brown, margins narrowly scarious. Perianth bristles 6-8, as long as or longer than nut, brown; stamens 2-3, anthers 0.5-0.7 mm; stigmas 2. Nut 0.8-1 x 0.6-0.8 mm (excl. stylopodium), obovoid, bi-convex, apex rounded, basal part gradually tapering, obscurely reticulate, glossy, finally black; stylopodium 0.1-0.2 x 0.3-0.4 mm, much wider than long, white, clearly constricted from nut.

Distribution: Pantropical extending into subtropics; Europe (Italy), Africa, Madagascar, Egypt, from Iraq to Pakistan, India, China, Taiwan, Malaysia, Australia, N and S America.

Ont.; Ala., Ariz., Calif., Fla., Ga., Ill., Ind., La., Mich., Miss., Nebr., Nev., N.Mex., Ohio, Okla., Pa., Tex.; Mexico; West Indies; Bermuda; Central America; South America; Asia; Africa; Pacific Islands.

Fl. Per.: April -June.

Fruiting spring–winter (Mar–Dec).

Rice fields, marshlands, wet meadows.

Brackish creeks, canal banks, dune depressions, hammocks, irrigation ditches, lakeshores, lagoons, mangrove thickets, maritime mud flats, ditches, salt marshes; 0–1500m.

Scirpus geniculatus L., Sp. Pl. 1: 48. 1753; E. caribaea (Rottb.) Blake in Rhodora 20: 24. 1918; Scirpus caribaeus Rottb., Descr. Pl. Rar.: 24. 1772; E. capitata R.Br., Prodr. 1: 225. 1810; C.B.Clarke in Hook.f., l.c. 627, non Scirpus capitatus L.; E. caduca (Del.) Schultes, Mantissa 2: 88. 1824; Scirpus caducus Del., Descr. Egypte, Hist. nat. 9 (1813 n.v.); K.M. Matthew, Fl. Tamilnadu Carnatic 4: pl. 654. 1988.

Scirpus geniculatus Linnaeus, Sp. Pl. 1: 48. 1753; Eleocharis capitata R. Brown; E. caribaea (Rottbøll) S. F. Blake; E. dispar E. J. Hill

Eleocharis caribaea (Rottb.) Blake, Rhodora 20 : 24. 1918.
Scirpus geniculatus L. Sp. PI. 48. 1753, in part. Not 5". geniculatus L. Sp. PI. ed. 2. 71. 1762.* Scirpus caribaeus Ro ttb. Descr. PI. Rar. 24. 1772. (West Indies.)
* See note under E. elegans. Scirpus geniculattts minor Vahl, Enum. 2: 251. 1805.
Eleocharis capitala R. Br. Prodr. 225. 1810. (Australia.)
Eleocharis setacea R. Br. Prodr. 225. 1810. (Australia.)
Eleocharis geniculata R. & S. Syst. Veg. 2: 150. 1817.
Eleocharis caditca Schultes in R. & S. Syst. Veg. Mant. 2 : 88. 1824. (Egypt.)
Scirpus Brownii Spreng. Syst. 1 : 204. 1825.
Eleogetnis capitatus Nees in Wight, Contr. Bot. Ind. 112. 1834.
Eleocharis microforniis Buckl. Proc. Acad. Phila. 1862 : 10. 1862. (Northern Texas.)
Eleocharis dispar E. J. Hill, Bot. Gaz. 7: 3. 1882. (Indiana.)
Chlorocharis capitata Rikli, Jahrb. Wiss. Bot. 27 : 564. 1895.
Eleocharis capitata var. dispar, Fernald, Rhodora 8: 129. 1906.
Eleocharis caribaea var. dispar Blake, Rhodora 20: 24. 1918.
Eleocharis caribaea var. Stokesii F. B. H. Brown, Bishop Mus. Bull. 84: 106. 1931. (Polynesia.)
Cespitose ; culms firm, 0.3-4 dm. high, striate and sulcate ; sheaths prominent, stramineous, usually with a brown base and a firm, oblique, often attenuate apex ; spikelets subglobose or ovoid, obtuse, many-flowered ; scales ovate-orbicular, almost cartilaginous to membranous, yellow to pale brown ; style bifid ; stamens 2 or 3 ; achene obovoid, 0.7-1 mm. long, lustrous-black to purplish, the spongy, whitened style-base variable in shape but usually much depressed; bristles 6-8, coarse, brown, exceeding the achene or occasionally lacking.
Type locality : Jamaica.
Distribution : South Carolina, Florida, Texas, California, Indiana, Michigan, Ontario ; tropics of the Old and New Worlds. The most widely distributed species of Eleocharis.

Eleocharis sintenisii Bock. Beitr. Cyp. 1 : 16. 1888
Eleocharis Shaferi Britton, Mem. Torrey Club 16 : 59. 1920. (Oriente, Cuba.)
Eleocharis yunquensis Britton; Britton & Wilson, Sci. Surv. Porto Rico 5: 92. 1923. (Puerto
Rico.) Heleocharis Ekmanii Kiikenth. Repert. Sp. Nov. 23 : 192. 1926. (Cuba.) Heleocharis debilis f. macra sensu Kiikenth. Repert. Sp. Nov. 23 : 192. 1926. (Brazil.)
Rootstocks wide-creeping to matted-lignescent ; culms filiform, O.S-3 dm. long, often short and rigid, irregularly sulcate ; sheaths stramineous to purple, the apex acute, not inflated ; spikelets usually few-flowered, elliptic-lanceolate to ovate, obtuse to acute ; scales obtuse to subacute, stramineous to purple, often with a green midrib ; stamens 2 or 3, anthers 0.4-0.7 mm. long; style bifid; achenes lenticular, narrowly obovoid, 0.9-1.5 mm. long, shiningblack ; style-base conic to subulate ; bristles light brown to white, equaling or exceeding the achene.
Type locality : "Prope Bayamon ad Palo Seco in fossis," Puerto Rico.
Distribution: Cuba; Puerto Rico.

Eleocharis geniculata is a species of spikesedge known by several common names, including bent spikerush and Canada spikesedge. This is a widespread plant of wet areas in the Americas, Asia, Africa, Australia, Madagascar, and some Pacific Islands. It is an annual spikesedge growing to a maximum height of about 40 centimeters. It has a few straw-colored leaves and many thin erect stems. The stems hold inflorescences of rounded spikelets each containing at least 10 tiny flowers. The flowers are covered with dark greenish-brown bracts. The fruit is a shiny purple-brown achene not more than a millimeter long.

Eleocharis geniculata là loài thực vật có hoa trong họ Cói. Loài này được (L.) Roem. & Schult. mô tả khoa học đầu tiên năm 1817.

弯形蔺（学名：Eleocharis geniculata）为莎草科荸荠属下的一个种。