Isolépis Sétacé

Isolepis setacea belongs to a distinct group of species characterized by ridged achenes (A. M. Muasya et al. 2001). Isolepis setacea was collected in 1874 on waste at Camden, New Jersey, and in the 1880s at Philadelphia, Pennsylvania; it has not persisted in the East. It has been known from the Pacific Coast since at least 1921. It is reported as native to Eurasia and Africa. It is cultivated as an ornamental.

The species is readily distinguished as small annual with small pseudolateral inflorescence and the lowest bract only slightly longer than the inflorescence; it also has leaf blades resembling the stem, but attached to sheaths surrounding stem base.

Plants perennial (annual?), forming dense mats; rhizomes creeping; culms, leaves, and bracts orange-punctate at 10–15X. Culms 3–25 cm × 0.2–0.3 mm. Leaves: sheaths usually reddish proximally; distal blade rudimentary to 6 cm × 0.2–0.5 mm. Inflorescences: involucral bracts 1 or 2; proximal bract erect to spreading, 3–10(–20) mm; distal bract reflexed, to 5 mm. Spikelets 3–6 × 2 mm; scales partly orange- to red- or blackish brown, midrib greenish to stramineous, not gibbous, prominently ribbed near midrib, often with 1+ pale veins on dark sides, 1.2–1.6 × 0.6–1 mm, membranous, hyaline, apex rounded to obtuse, mucro to 0.1 mm; proximal scale like others. Flowers: anthers 0.3–0.5 mm; styles 3-fid or 3-fid and 2-fid. Achenes falling separately from floral scales, orange-brown, each face prominently longitudinally 5–8-ribbed, many fine transverse ridges evident at 20–30X, broadly obovoid to oblong, thickly biconvex to compressed-trigonous, abaxial angle obscure, lateral angles prominent, faces convex, 0.8–1 × 0.5 mm. 2n = 28.

Annual, forming small tussocks, 2.5-20 cm. Roots fibrous. Stem 0.2-0.3 mm diam., terete, smooth, green or yellowish green. Leaves reduced, usually with one complete leaf at stem base; sheaths to 20 mm, lowest bladeless, scarious, often reddish; longest much overtopping lower ones, yellow green or lower part often reddish, mouth wide, scarious, oblique; blades 1-20 mm, as wide as stem, channelled, smooth, apex obtuse. Inflorescence 1-2 sessile spikes; bract as long as spike or to 10 mm, basal part (sheath) scarious, keeled, often reddish brown. Spikes 2-5 mm, globose or ovoid, with up to c. 30 glumes; when two spikes, lower with obtuse, glume-like prophyll; glumes 1.3-1.5 mm, cymbiform, keeled, midnerve strong, at first green, smooth, barely reaching obtuse apex, sides with 3-5 fine nerves, reddish brown or sometimes colourless, scarious. Stamens 2; stigmas 3. Nut 0.7-0.9 x 0.5-0.6 mm, with wide stipe and narrow beak c. 0.1 mm, obovoid, unequally bi-convex, brown, sometimes whitish, trabeculate with pronounced longitudinal ribs.

Eurasia, Australia.

introduced; B.C.; Calif., Oreg., Wash.; Eurasia; Africa; Australia (including Tasmania); New Zealand.

Distribution: Europe, N Africa, mountains of E Africa, southern Africa, Lebanon, Syria, Turkey, Caucasus, Kazakhstan, Uzbekistan, Tadjikistan, W China, in SW Asia from NW Iran to Pakistan and east to Sikkim; introduced to western N America and Tasmania.

2200-3800 m

Fl. & Fr.: June - July.

Fruiting late spring–fall.

Stream banks, pond margins, ditches, coastal, rarely inland; 0–1500m.

By water courses, in boggy places with moving water; 700-3200 m.

Scirpus setaceus Linnaeus, Sp. Pl. 1: 49. 1753

Scirpus setaceus L., Sp. Pl. 1: 49. 1753; C.B.Clarke, l.c. 654; R.R.Stewart l.c. 103; Schoenoplectus setaceus (L.) Palla, in E. Hallier & A. Brand (eds.), W.D.J. Koch, Syn. Fl. Germ., ed. 3, 3: 2538. 1905; Madalski, Fl. Polon. Terr. Adiac. Icon. 3(1): 258. 1979; Uniyal & al., Cyperaceae Uttar Pradesh: 38 1997.