Rhynchospora nivea
Rhynchospora harperi
showy whitetop
Harper's beaksedge
erect to spreading-ascending, leafybased, trigonous or compressed, ribbed.
erect to excurved, leafybased, narrowly linear, ± terete.
exceeded by scape;
blades narrowly linear to filiform, 0.2–2 mm wide, apex tapering, trigonous.
shorter than culm;
blades ascending, narrowly linear, proximally flat or margins slightly involute, 0.5–1(–2) mm wide, distally canaliculate, apex trigonous, tapering, subulate.
terminal, solitary, headlike, dense, white, leafyinvolucrate, hemispheric to globose, 0.5–1.5 cm wide;
involucral bracts (0–)1–4, ascending to recurved, green, (0.7–)2–5(–6) cm × 0.2–2 mm.
spikelet clusters 1–3, laterals 0–2, all turbinate to hemispheric, terminal internode usually excurved; leafy bracts setaceous, overtopping inflorescence.
white, ovoid, 5–7 mm;
fertile scales several, boat-shaped, 2.5–3.5 mm, keel curved, not sharp.
redbrown, lanceoloid, 5–7 mm, apex acute;
fertile scales lanceolate, (2.5–)4–5 mm, apex acute to acuminate;
midrib paralleled by several indistinct ribs, excurrent as short awns.
perianth absent.
bristles 6, reaching from mid tubercle to beyond tip.
0.8–1 mm;
body yellow to near black, broadly pyriform-obovoid, tumidly lenticular, 0.5–0.8 × 0.5–0.8 mm, margin narrow, flowing into tubercle;
surfaces transversely sharply wavyrugose, ridges bordered by rows of fine, linear, vertical lattices;
tubercle depressedtriangular, lunate-based, shortbeaked 0.2(–0.3) mm, gray-crustaceous.
3(–4) per spikelet, 2.1–2.5 mm;
stipe and receptacle 0.2–0.3 mm, sparsely setose and setulose;
body glossy, brown with pale center, obovoid-lenticular, 1.1–1.5 × 1–1.1 mm, surfaces finely longitudinally lined, variably low papillatecancellate, also often transversely with wavy lines of dark dots;
tubercle flattened, triangular-subulate, (0.8–)0.9–1(–1.1) mm, setulose-ciliate.
Rhynchospora nivea
Rhynchospora harperi
Rhynchospora nivea, of the “Dichromena” of North America, is the smallest fruited and most slender and has the fewest and shortest involucral bracts (in some plants the bract is entirely absent). Involucral bracts of R. nivea are almost entirely green.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Rhynchospora harperi is most abundant in a very special habitat referred to here as the “Hypericum pond.” These are typically shallow ponds in pine savannas, frequently ringed by stands of Nyssa, Taxodium, Ilex, and Cyrilla, but most of the pond itself is dominated by one or more myriandrous shrubby Hypericum species. Here R. harperi is distinguished from other species by the often abrupt bend of its ultimate internode.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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