Rhynchospora latifolia
Rhynchospora plumosa
sandswamp whitetop
plumed beaksedge
arching or erect, leafy-based, distally wandlike, terete, multiribbed.
erect or excurved, filiform to linear.
ascending to spreading, overtopped by scape;
blades linear, proximally flat, 2.5–5 mm wide, apex subulate, trigonous.
erect or excurved, shorter than scape;
blades filiform to linear, to 1.5 mm wide, margins involute, apex trigonous, 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 1–several, dense or sparse, when several, either widely spaced or close together, if widely spaced then ovoid to hemispheric, if close together then lobed ellipse or cylinder; leafy bracts filiform, setaceous, overtopping each cluster.
white, ovoid, 5–7 mm;
fertile scales boatshaped, sharply curved-keeled, 5 mm, apex acute.
light redbrown to deep brown, broadly fusiform to ovoid, (2.5–)3.5–4 mm, apex acute to acuminate;
fertile scale broadly ovate, strongly convex, (1.5–)2–3 mm, apex acuminate to mucronate, midrib excurrent or not.
perianth absent.
perianth bristles 6, plumose, reaching at least to fruit midbody, often to tubercle tip.
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, (1.5–)2–2.5 mm;
body redbrown or brown, tumidly obovoid or ellipsoid, sometimes obscurely lenticular, (1.2–)1.3–1.8(–2) × 1–1.5 mm;
surfaces interruptedly crossrugulose;
tubercle narrowly to broadly conic, mostly 0.3–0.5 mm, base flaring, round or indistinctly 2lobed.
= 12.
Rhynchospora latifolia
Rhynchospora plumosa
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.)
Particularly in Gulf Coastal Plain savannas, Rhynchospora plumosa appears to have two distinct morphs: one very densely cespitose with filiform leaves, filiform, arching culms, and spikelets in short, broad, dark brown clusters, and the other morph taller, stiffer, with broader leaves and culms, and longer, sharper, paler spikelets in narrow compounds of clusters. After many attempts to do what others have—namely to create two distinct species—I have had to retrench, because so many intergrades occur.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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