Eleocharis atropurpurea, (Retz.) C. Presi

Tutin, T. G., Heywood, V. H., Burges, N. A., Moore, D. M., Valentine, D. H., Walters, S. M. & Webb, D. A., 1980, Flora Europaea. Volume 5. Alismataceae to Orchidaceae (Monocotyledones), Cambridge: Cambridge University Press : 282-283

7. E. atropurpurea (Retz.) C. Presi , Reliq. Haenk. 1:196 (1828).

Like 5 but more delicate, with stems up to 10 cm and not more than 0-3 mm in diameter; spikelet 2-4 mm; nut c. 0-5 mm, shining, black; stylopodium minute, flattened and c. | as wide as nut; bristles never as long as fruit, often rudimentary or absent. Sandy ground, seasonally inundated. Italy, S. Switzerland. *He *It.

Widespread in the tropics and subtropics and perhaps introduced in Europe, where it was first recorded in 1830.

A related species, E. geniculata (L.) Roemer & Schultes , Syst. Veg. 2: 150 (1817) ( E. caduca (Delile) Schultes ), also widespread in the tropics, has been recorded from Italy, Sicilia and Sardegna. It differs most clearly in the larger nut (c. 1 mm).

E. olivacea Torrey , Ann. Lyc. New York 3: 300 (1836), from E. North America, and E. flavescens (Poiret) Urban , Symb. Antill. 4: 116 (1903), from Central America, have both been recorded as weeds in rice-fields in N. Italy and Portugal; they have a greenish-brown nut c. 1 mm, with a conical stylopodium. (8-13). E. palustris group. Perennial, rhizomatous plants very variable in size; stems up to 100 cm, 1-8 mm in diameter. Uppermost leaf-sheath almost transversely truncate; leaf-sheaths and stem-bases often reddish or purplish. Spikelet 3-30 mm, many-flowered, pale straw-coloured to dark brown; lowest glume empty, encircling base of spikelet, or 2 lowest glumes empty,

each half-encircling. Stamens 3. Stigmas 2. Nut 1-2-2-2 mm, biconvex, obovate or elliptical, more or less finely punctate, pale yellow to dark brown; stylopodium very variable, but always constricted at junction with nut. Bristles (0)4-8, variably developed.

A widespread group in which taxonomic difficulty is partly attributable to polyploidy and hybridization. The following treatment distinguishes at least the more important European taxa. 1 Only the lowest glume of spikelet empty, encircling base of spikelet 2Stylopodium minute, c. i as wide as nut; lowest glume up to i as long as spikelet 13. oxylepis 2 Stylopodium at least | as wide as nut; lowest glume rarely more than | as long as spikelet 12. uniglumis 1 Two lowest glumes of spikelet empty, subequal, and each halfencircling base of spikelet 3 Stylopodium at least twice as long as wide 10. austriaca 3 Stylopodium less than twice as long as wide 4 Stylopodium longer than wide; bristles 4, rarely 0 8. palustris 4 Stylopodium wider than long; bristles 4-8 5 Bristles 4(—5); glumes usually with wide hyaline margin

9. mitracarpa 5 Bristles (5—)6—8; glumes with narrow hyaline margin

11. mamillata