Isolepis

Herbs, annual or perennial, cespitose, rhizomatous or not, smooth, glabrous. Culms terete. Leaves all basal; sheaths green to stramineous, sometimes reddish proximally; ligules absent; blades rudimentary to exceeding culms. Inflorescences terminal, sometimes pseudolateral, capitate or solitary spikelet; spikelets 1–3(–15); involucral bracts 1(–2), spreading to erect, like foliage leaf blades. Spikelets: scales 8–25, spirally arranged, each subtending flower. Flowers bisexual; perianth absent; stamens 1–3; styles linear, 2–3-fid, base persistent, sometimes slightly enlarged. Achenes biconvex or trigonous, papillose or longitudinally ribbed.

Distribution

Worldwide in cool-tropical and temperate regions, especially Africa and Australia.

Discussion

Species 69 (4 in the flora).

Isolepis is difficult to delimit on a worldwide basis and has been included in Scirpus in the broad sense. Data derived from embryologic, genetic, and other studies led in recent years to the acceptance of Isolepis as a distinct genus (J. J. Bruhl 1995; P. Goetghebeur 1998; A. M. Muasya et al. 2001).

Selected References

Muasya, A. M. 1998. Systematics of the Genus Isolepis R. Br. (Cyperaceae). Ph.D. thesis. University of Reading.

Muasya, A. M., D. A. Simpson, M. W. Chase, and A. Culham. 2001. A phylogeny of Isolepis (Cyperaceae) inferred using plastid rbcL and trnL-F sequence data. Syst. Bot. 26: 342–353.

Muasya, A. M. and D. A. Simpson. 2002. A monograph of the genus Isolepis R. Br. (Cyperaceae). Kew Bull. 57: 257–362.

Lower Taxa

Isolepis carinata, Isolepis cernua, Isolepis pseudosetacea, Isolepis setacea

Key

1	Spikelets with scales markedly gibbous, often clasping shed achenes, colorless to stramineous, or orangish, or greenish; achenes acutely equilaterally trigonous; leaf sheaths green to stramineous or brown.	> 2
1	Spikelets with scales neither gibbous nor clasping shed achenes, usually at least partly orange- to red-brown or blackish; achenes compressed-trigonous or thickly plano-convex; leaf sheaths usually reddish proximally.	> 3
2	Scales from middle of spikelet 1.8–2 mm, with awns 0.2–0.5 mm; achenes 1–1.5 mm.	Isolepis carinata
2	Scales from middle of spikelet 1–1.2 mm, with mucros to 0.1 mm; achenes 0.7–0.9 mm.	Isolepis pseudosetacea
3	Achenes papillose, not ribbed; culms, leaves, and involucral bracts not orange-punctate or sheaths sparsely so.	Isolepis cernua
3	Achenes not papillose, prominently longitudinally ribbed at 10X and minutely transversely ridged at 20–30X; culms, leaves, and involucral bracts orange-punctate at 10– 15X.	Isolepis setacea