Rhynchospora oligantha
Rhynchospora perplexa
featherbristle beaksedge
pineland beaksedge
filiform, leafy at base, wiry.
lax, often excurved, slender, ± terete or 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.
ascending, exceeded by culm;
blades linear, proximally flat, 1.5–2.5 mm wide, apex trigonous, subulate, tapering.
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.
clusters 3–4, widely spaced, narrowly, compactly, or diffusely turbinate; leafy bracts exceeding proximal clusters.
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.
deep redbrown, ovoid to broadly ellipsoid, 2–3 mm, apex acute to acuminate;
fertile scales broadly elliptic to obovate or orbiculate, 1.4–2(–2.5) mm, apex rounded to notched, midrib shortexcurrent.
perianth bristles 6, reaching to or slightly past tubercle base, increasingly plumose from middle to base.
perianth bristles 0–3, vestigial when present.
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.
2–4 per spikelet, 1.5 mm;
body pale brown to brown, strongly flattened, orbicular to broadly obovoid, 1–1.3 × 0.9–1.2 mm, surfaces sharply transversely wavyrugose, intervals finely vertically striate with rows of linearrectangular alveolae;
tubercle depressed, triangular, flattened, 0.2–0.3 mm, base lunate.
Rhynchospora oligantha
Rhynchospora perplexa
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.)
In habit and in shape, size, and color of spikelet, Rhynchospora perplexa strongly resembles R. microcarpa, a species with which it is commonly associated in the Coastal Plain. An examination of the fruit shows those of R. perplexa to be flattened, with fewer and much coarser transverse ridges, the intervals with very narrow vertical alveolae. The perianth in most instances is absent or rudimentary. Fruit of R. microcarpa is biconvex with more transverse ridges (eight or more), the intervals more coarsely alveolate; its perianth bristles are six, evident, extending at least halfway up the fruit body.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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