Rhynchospora latifolia
Rhynchospora oligantha
sandswamp whitetop
featherbristle beaksedge
arching or erect, leafy-based, distally wandlike, terete, multiribbed.
filiform, leafy at base, wiry.
ascending to spreading, overtopped by scape;
blades linear, proximally flat, 2.5–5 mm wide, apex subulate, trigonous.
ascending to erect;
blades filiform, nearly terete, or channeled, sometimes compressed, nearly reaching distal inflorescence or much shorter, 0.2–0.3 mm thick, apex subulate.
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.
spikelet clusters 2–6, simple or reduced to 1 spikelet, branches ascending to divaricate or reflexed; leafy bracts single per cluster, filiform, setaceous, with clusters appearing lateral to bracts.
white, ovoid, 5–7 mm;
fertile scales boatshaped, sharply curved-keeled, 5 mm, apex acute.
pale redbrown, ellipsoidlanceoloid, 5–6(–8) mm, apex acute to acuminate;
fertile scales oblongelliptic, convex, acuminate, 3.5–5 mm, apex broadly acute, midrib forming apiculus.
perianth absent.
perianth bristles 6, reaching to or slightly past tubercle base, increasingly plumose from middle to base.
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.
1–3 per spikelet, (2.5–)2.7–3(–3.4) mm;
body light brown to brown, ellipsoidobovoid, distally conspicuously necked, tumidly lenticular, 1.7–2.5 × 1.5–1.8 mm;
surfaces smooth or minutely transversely rugulose;
tubercle conicsubulate, 0.5–0.7 mm, base flaring.
= 12.
Rhynchospora latifolia
Rhynchospora oligantha
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.)
Rhynchospora oligantha is distinguished from other taxa of its complex mostly by the distinctive neck at the achene apex, a feature essentially absent in R. breviseta, its closest relative. Those two species have been heavily impacted by conversion of pine savannas to cropland or pine plantations; even with abandonment or clearing of such land, they are very slow to reoccupy the disturbed sites.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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