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Published In: Prodromus Florae Novae Hollandiae 221–223. 1810. (Prodr.) Name publication detailView in BotanicusView in Biodiversity Heritage Library

Project Name Data (Last Modified On 9/1/2009)
Acceptance : Accepted

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9. Isolepis R. Br.

Plants annual (perennial elsewhere), tufted, glabrous. Aerial stems few to usually many per plant, 1–20 cm long, erect to spreading or arched, slender, unbranched, circular or somewhat flattened in cross-section, finely ridged. Leaves basal, the sheaths papery, light green to tan toward the base, the sheath apices truncate or convex, the ligule absent, the leaf blades mostly shorter than to as long as the stems, 0.3–0.5 mm wide, spreading to ascending or more commonly arched, the margins curled inward except toward the tip. Inflorescences appearing lateral, subtended by 1 erect, stemlike bract (rarely a second, highly reduced bract present), composed of 1–3 spikelets, these 2–7 mm long, 1–2 mm in diameter, ovate in outline, usually pointed at the tip, sessile or nearly so. Florets 4–14 per spikelet, in an overlapping spiral pattern (sometimes appearing 2-ranked in reduced spikelets), perfect. Spikelet scales 1–3 mm long, broadly ovate, the tips rounded to pointed, strongly folded around the fruit, straw-colored to pale green or light tan, the midrib thickened (keeled) and extended past the main body of the scale as a short awn, usually green. Perianth bristles absent. Stamens 2–3. Styles not expanded at the base during flowering, not forming a tubercle, but frequently persisting on the fruit as a minute beak. Stigmas 3. Ovaries and fruits naked, without a perigynium (saclike covering). Fruits ovate in outline, sharply 3-angled. About 40 species, North America to South America, Europe, Asia, Africa, Australia, Pacific Islands.

Isolepis has been included in the genus Scirpus in most of the North American botanical literature. For further discussions of the segregation of genera from Scirpus, see the treatment of that genus and the review of Missouri bulrushes by Smith and Yatskievych (1996). The two Missouri taxa are quite similar morphologically and were classified as a single species until the description of I. molesta in 1964.


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1 Spikelet scales 1.7–3.0 mm long; fruits 1.0–1.5 mm long, orangish brown to brown, lacking a white, waxy coating 1 Isolepis carinata
+ Spikelet scales 1.0–1.5 mm long; fruits 0.7–0.9 mm long, pinkish brown to orangish brown, but this obscured by a white, waxy coating covering the fruit 2 Isolepis molesta
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