Rhynchospora latifolia
Rhynchospora chalarocephala
sandswamp whitetop
loosehead beaksedge
arching or erect, leafy-based, distally wandlike, terete, multiribbed.
erect to ascending-arching, slender, nearly terete, multiribbed.
ascending to spreading, overtopped by scape;
blades linear, proximally flat, 2.5–5 mm wide, apex subulate, trigonous.
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 3–7, widely spaced, clusters loosely turbinate to hemispheric, to 1.3 cm wide.
white, ovoid, 5–7 mm;
fertile scales boatshaped, sharply curved-keeled, 5 mm, apex acute.
brown to pale red-brown, lance-fusiform, 3–5.5 mm;
fertile scales elliptic, 2.5–4 mm, acute, midrib short-excurrent.
perianth absent.
perianth bristles 6, ± equaling tubercle.
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 per spikelet, (2.5–)2.7–3.3(–3.5) mm, body pale brown with yellowish center, ± broadly oblong-obovoid distal to stipe, lenticular, 1.5–2 × 0.8–1 mm;
tubercle narrowly triangularsubulate, (1–)1.2–1.5(–2) mm, less than 0.5 mm wide at base.
leaves exceeded by culm;
blades flat, linear, 1–2 mm wide, apex tapering, trigonous.
= 12.
Rhynchospora latifolia
Rhynchospora chalarocephala
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.)
Some specimens of Rhynchospora chalarocephala are very difficult to distinguish from R. microcephala, and unquestionably intergrades occur in peninsular Florida and the Gulf southern coastal plain. Rhynchospora chalarocephala tends to have longer, paler, narrower spikelets in looser clusters; the dilated part of the fruit body has a narrower, more oblong outline; and the tubercle is both narrower with a narrower base and longer (mostly 1–1.5 mm versus 0.9–1.2 mm in R. micro-cephala). Most material is easily sorted because R. chalarocephala has paler spikelets in turbinate to hemispheric clusters; the dark brown spikelets of R. microcephala are in globose heads.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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