Rhynchospora debilis
Rhynchospora oligantha
savannah beaksedge
featherbristle beaksedge
erect to arching or spreading, leafy, ± filiform, ± terete, stiff to rather lax.
filiform, leafy at base, wiry.
exceeded by culm;
blades linearfiliform, proximally shallowly concave, 1 mm, apex tapering, trigonous, blunt or broadly acute.
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.
spikelet clusters 1–2, mostly compact, turbinate to hemispheric; leafy bracts setaceous, exceeding spikelet clusters.
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.
dark redbrown, ovoid, 2–3 mm, apex acute;
fertile scales obovate, 1.5–1.7(–2) mm, apex broadly rounded or retuse, midrib excurrent as cusp or mucro to 0.5 mm.
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.
bristles 6 or vestigial, rarely reaching fruit midbody, antrorsely barbellate.
perianth bristles 6, reaching to or slightly past tubercle base, increasingly plumose from middle to base.
1–2 per spikelet,1.7–2 mm;
body brown with large pale center, lenticular, broadly obovoid to ± orbicular, 1.2–1.5 × 1.4–1.6 mm;
tubercle flat, triangular, concave-sided, 0.4–0.6 mm, sometimes apiculate.
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.
Rhynchospora debilis
Rhynchospora oligantha
Rhynchospora debilis is very similar to R. wrightiana except it has smaller spikelet clusters and more depressed fruit tubercles. It is a common invader of cutover and bulldozed low pineland where it assumes a lowspreading habit, its many culms radiating from the common center much like spokes in a wheel.
(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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