Flora of North America species comparison

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Isolepis

bulrush, club-rush
Habit 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.

Isolepis
Distribution
from USDA
Worldwide in cool-tropical and temperate regions; especially Africa and Australia
[BONAP county map]
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).

(Discussion copyrighted by Flora of North America; reprinted with permission.)
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.
I. carinata
2. Scales from middle of spikelet 1–1.2 mm, with mucros to 0.1 mm; achenes 0.7–0.9 mm.
I. pseudosetacea
3. Achenes papillose, not ribbed; culms, leaves, and involucral bracts not orange-punctate or sheaths sparsely so.
I. 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.
I. setacea
Source FNA vol. 23, p. 137. Author: S. Galen Smith.
Parent taxa Cyperaceae
Subordinate taxa
I. carinata, I. cernua, I. pseudosetacea, I. setacea
Synonyms Scirpus section I.
Name authority R. Brown: Prodr., 221. (1810)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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