9. Isolepis R. Br.
(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.
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.