Rhynchospora latifolia
Rhynchospora megalocarpa
sandswamp whitetop
sandyfield beaksedge
arching or erect, leafy-based, distally wandlike, terete, multiribbed.
erect to arching, leafy, trigonous, slender, firm.
ascending to spreading, overtopped by scape;
blades linear, proximally flat, 2.5–5 mm wide, apex subulate, trigonous.
overtopped by culms;
blades linear, proximally flat, 3–7 mm wide, apex trigonous, subulate, tapering.
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, sparse, widely spaced, turbinate;
peduncles and branches ascending; leafy bracts exceeding proximal clusters.
white, ovoid, 5–7 mm;
fertile scales boatshaped, sharply curved-keeled, 5 mm, apex acute.
light redbrown, ovoid to ellipsoid, (4–)5–8(–9) mm, apex acute or acuminate;
fertile scales ovate, (5.5–)6–6.5(–7) mm, midrib included or shortexcurrent.
perianth absent.
perianth bristles 6(–8), mostly reaching from fruit midbody to tubercle base, 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, (3.5–)4–5 mm;
body dark brown to mahogany or nearly black, broadly obovoid, tumid, nearly smooth, buttressed to tubercle;
tubercle lowconic, rimmed, 0.7(–1) mm, apex apiculate.
= 12.
Rhynchospora latifolia
Rhynchospora megalocarpa
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.)
The perianth in Rhynchospora megalocarpa is unusual. The receptacular joint is stubby, bearing staggered cycles of bristles that vary extremely in length and number—on a par with R. alba, R. baldwinii, and R. macra in numbers of bristles. The greatest extreme is twelve, the fewest as low as two; usually if the number is low, the remaining sites for bristles will be dark-colored nubbins.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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