keys to the vascular plants of east texas - Botanical Research ...

632 CYPERACEAE/RHYNCHOSPORA
following Kral (2002c) in recognizing it as a distinct species. It is of conservation concern.
(RARE 2001, 2002b: G3S3) E �
Rhynchospora inexpansa (Michx.) Vahl, (not expanded, not spreading), NODDING BEAK SEDGE,
NODDING BEAK-RUSH. Tufted perennial 0.3–1.2 m tall; inflorescences with spikelet clusters on
flexuous, often drooping stalks; spikelets 5–7(–9) mm long; bristles clearly surpassing the tubercle;
achenes 2–2.5 mm long, narrowly oblong-ellipsoid, flattened; tubercle 0.8–1.2 mm long.
Open pinelands, other low open areas; widespread in se part of East TX w to Montgomery and
Walker cos. and n to Panola (Turner et al. 2003) cos.; also n margin of Gulf Prairies and Marshes;
se U.S. from VA s to FL w to AR and TX. Jun–Oct.
Rhynchospora latifolia (Baldwin ex Elliott) W.W. Thomas, (broad-leaved), GIANT WHITE-TOP,
SANDSWAMP WHITE-TOP. Rhizomatous perennial 25–125 cm tall; leaves mostly on basal half of
culm; inflorescence a dense, hemispherical to globose head; bracts unequal in length, the
longer ones 5.5–13 cm long; white zone on bracts conspicuous, 2.2–5.5 cm long; spikelets 4.5–7
mm long, with white scales; achenes 1.2–1.5 mm long, broadly obovoid to orbicular or nearly so,
widest near middle, tumidly lenticular. Moist open areas, savannahs, acidic soils; se part of the
Pineywoods; also n Gulf Prairies and Marshes.; se U.S. from NC s to FL w to TX. May–Aug. Previously
separated into the genus Dichromena [as D. latifolia Baldwin ex Elliott] .This species is reported
to be pollinated by insects (Thomas 1984). Section Dichromena (WHITE-TOPS) is primarily
tropical—the evolution of insect pollination (white bracts, etc.) in this group may be an
adaptation that allowed the group to move into tropical forests where insect and self-pollination
can compensate for the lack of air movement and hence reduced wind pollination (Thomas
1984; Tucker 1987).
Rhynchospora macra (C.B. Clarke ex Britton) Small, (large, long), LARGE BEAK SEDGE, LARGE
BEAK-RUSH. Tufted perennial ca. 40–80 cm tall; inflorescences with spikelet clusters turbinate
to hemispheric; spikelets 4–5(–7) mm long, pale brown to nearly white; perianth bristles numerous
(16–20), longer than the achenes; achenes (1.7–)2–2.1(–2.2) mm long, obovoid, lenticular;
tubercle 0.8–1 mm long. Bogs and seeps, sandy soils; Robertson, Wood (BRIT), Houston (Gale
1944), Angelina, Jasper (MacRoberts & MacRoberts 1998a), Anderson, Freestone, Leon, and
Newton (J. Singhurst, pers. comm.) cos.; se U.S. from SC s to FL w to TX. Aug–Oct. The spikelets
of this species can sometimes be nearly white. However, R. macra is quite different from the
truly white-spikeleted species (R. colorata, R. latifolia, and R. nivea), in that its bracts never
have a basal white zone. This species is of conservation concern. (RARE 2001, 2002b: G3S1) �
Rhynchospora macrostachya Torr. ex A. Gray, (large-spiked), TALL BEAK-RUSH, HORNED BEAK-
RUSH, TALL HORNED BEAK SEDGE. Coarse perennial to 1.5(–1.7) m tall, similar to R. corniculata except
for the longer bristles subtending the achenes; also inflorescence branches usually more
stiffly erect rather than spreading, with spikelets usually in distinct tight clusters from the
middle and upper nodes; spikelets strikingly elongate, to 26 mm long (including exserted tubercles);
bristles usually 6, mostly 10–12 mm long, antrorsely barbed; achenes 5–6 mm long,
obovoid, compressed; tubercle extremely conspicuous, 15–20 mm long. Shorelines, swamps,
other wet areas; scattered in se part of East TX in Pineywoods and Post Oak Savannah and to
the n in Red River drainage; also n Gulf Prairies and Marshes; widespread in e 1/2 of the U.S.
May–Aug. [R. corniculata (Lam.) A. Gray var. colpophylla Fernald & Gale]
Rhynchospora microcarpa Baldwin ex A. Gray, (small-fruited), SOUTHERN BEAK SEDGE. Tufted
perennial to 100 cm tall; inflorescences variable, the spikelet clusters often dense; spikelets 2–3
mm long; achenes 1–1.2 mm long, obovoid to globose, lenticular; tubercle 0.2–0.3 mm long. Wet
areas; included based on citation for the Big Thicket National Preserve by National Park Service
(1995a, 1995b); the only confirmed TX locations we are aware of are from the s part of the Gulf
Prairies and Marshes—thus this species is possibly not a member of the East TX flora; se U.S.
from NC s to FL w to TX. Jun–Sep. [R. edisoniana Britton ex Small]