Rhynchospora latifolia
Rhynchospora corniculata
sandswamp whitetop
shortbristle horned beaksedge
arching or erect, leafy-based, distally wandlike, terete, multiribbed.
stiffly erect, leafy, triangular, multiribbed;
principal leaves overtopped by culm;
blades flat, 3–20 mm wide, apex attenuate, trigonous.
ascending to spreading, overtopped by scape;
blades linear, proximally flat, 2.5–5 mm wide, apex subulate, trigonous.
terminal, headlike clusters of spikelets, clusters dense, leafy-involucrate;
involucral bracts several, spreading to downcurved, longest 6–13 cm × 5–10 mm, mostly white to midbract, then green, abruptly narrowly linear.
terminal and axillary, diffuse clusters of corymbs, fascicles turbinate to hemispheric;
bracts often overtopping clusters.
white, ovoid, 5–7 mm;
fertile scales boatshaped, sharply curved-keeled, 5 mm, apex acute.
few to several per cluster, brown or reddish brown, lanceoloid, 10–15 mm, apex narrowly acute;
fertile scales broadly lanceolate, (7.5–)10–13(–14) mm, apex acute, midrib shortexcurrent or not.
perianth absent.
perianth bristles 5–6, longest reaching to or slightly beyond fruit midbody, antrorsely barbellate.
several per spikelet, 1.5–2 mm;
body yellowish to deep brown, tumidly lenticular, broadly obovoid to orbicular or oblate, 1.5 mm, widest at or toward midbody, margins flowing to tubercle;
surfaces with many fine rows of vertical shallow lattices, their contiguous ends making transverse rows of papillae;
tubercle crescent-based, depressed-triangular, 0.5 mm, apex acute.
1(–2) per spikelet, 13–20(–25) mm;
body oblongellipsoid, compressed, 4–5(–6) × 2–3 mm, base narrowed, short, margins thickened, often crimped, surfaces concave, striate, minutely cancellate or pebbled;
tubercle subulate, 2-grooved, 10–15(–20) mm, scabridulous.
= 12.
= 18.
Rhynchospora latifolia
Rhynchospora corniculata
A specimen collected near Tullahoma, Tennessee, reported as Dichromena latifolia (A. Gattinger 1901), was later destroyed by fire. I did not see the specimen, nor was a description of it published. Because extant populations of the similar Rhynchospora colorata are just over the border in Alabama, that species is likely to have been the one found by Gattinger.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Specimens of Rhyncospora corniculata with base of the tubercle fully as wide as the fruit and with fruit bodies at the lower length range were treated by M. L. Fernald as R. corniculata var. interior Fernald.
The percent of fruit with crimped margins in Rhynchospora corniculata increases westward in the Gulf coastal plain; toward Mexico it is sympatric with R. indianolensis and R. gigantea, which also have crimped fruit.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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