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

592 CYPERACEAE/ELEOCHARIS
Eleocharis brittonii Svenson ex Small, (for Nathaniel Lord Britton, 1859–1934, botanist at NY
Botanical Garden), BRITTON’S SPIKE-RUSH. Tufted annual similar to E. microcarpa; culms 37 cm
or less tall; spikelets ca. 2–10 mm long, ellipsoid to ovoid, with 13–76 scales, sometimes proliferating
vegetatively; lowermost scale of spikelet different from other scales, usually longer and
often resembling an involucral bract, rounded apically; achenes trigonous, ca. 0.5–0.6 mm long;
tubercles tiny, 0.1 mm or less long. Wet areas including ponds and swamps, sometimes emergent;
Austin, Hardin, Houston, Jasper, Montgomery, and Newton (S.G. Smith, pers. comm. of
data from Jeremy Bruhl) cos.; also n Gulf Prairies and Marshes and Hockley Co. in the High
Plains; because distributional data for this species was obtained after map pages for the flora
were completed, no county distribution map is provided; se U.S. from SC s to FL w to MO and
TX. Spring–fall. [E. microcarpa var. brittonii (Svenson ex Small) Svenson] This species has sometimes
been included in the similar E. microcarpa (e.g., Correll & Johnston 1970). Without (or
even with) achenes the two are often difficult to distinguish. Bruhl and Smith (2002) indicated
that preliminary phenetic studies suggest some plants from the se U.S. (FL w to TX), while related
to E. brittonii, may represent another entity warranting taxonomic recognition; TX plants
at this time might thus better be called Eleocharis aff. brittonii. However, until further study is
done, we are treating the TX plants as E. brittonii.
Eleocharis cellulosa Torr., (from the cellular surface of the achene), GULF COAST SPIKE-RUSH.
Tufted rhizomatous perennial; culms erect, to 80 cm tall, (1–)3–5 mm wide; distal leaf sheath
apex narrowed on one side to a triangular point, this with an abrupt awl-like tip; spikelets cylindric,
usually 19–36(–50) mm long and (3–)3.5–5.6 mm thick, with many scales; scales of
spikelets 3–4.4 mm wide, broadly rounded, with a darker (brownish to reddish) submarginal
band; achenes biconvex, ca. 2–2.8 mm long, light brown; tubercle not at all basally constricted,
appearing as a continuation of the achene, 0.1–0.5 mm long. Mud, wet areas, shorelines; Grayson
(BRIT), Gonzales, Guadalupe, Jefferson, and Orange (Turner et al. 2003) cos., also Burnet Co.
(S.D. Jones, pers. comm.) in Cross Timbers and Prairies, Gulf Prairies and Marshes, and Edwards
Plateau; se U.S. from SC s to FL w to AR and TX. Spring–fall.
Eleocharis compressa Sull., (flattened), COMPRESSED SPIKE-RUSH, FLAT-STEM SPIKE-RUSH. Rhizomatous
perennial forming mats; culms strongly flattened or not so, 8–28(–45) cm tall; distal leaf
sheath apex nearly truncate; spikelets 3–8(–12) mm long, narrowly oblong or cylindric to narrowly
elliptic to ovoid, with 20–60 scales; scales with long-pointed scarious tips (often bifid, except
tip of lowermost scale of spikelet is entire); achenes trigonous, 0.8–1.2 mm long, yellow to
golden brown to brown; tubercle small, 0.3 mm or less long. The two varieties of E. compressa
have in the past been recognized as distinct species by most authorities. However, we are following
Smith (2002d) who indicated that the two taxa intergrade completely and are most appropriately
recognized at the varietal level.
1. Culms usually several-angled or -ribbed, not strongly flattened, 0.3–0.8 mm wide, 2 times or less
wider than thick ___________________________________________________________ var. acutisquamata
1. Culms strongly flattened, 0.5–1.8 mm wide, 2–5 times wider than thick ____________________ var. compressa
var. acutisquamata (Buckley) S.G. Sm., (with sharp-pointed, small, scale-like bracts or leaves),
SHARP-SCALE SPIKE-RUSH. Pond margins or low areas of prairies, calcareous soils; scattered in
East TX; also n Gulf Prairies and Marshes, Cross Timbers and Prairies, and Edwards Plateau; sw
Canada and c U.S. Late Mar–May(–Jul). [E. acutisquamata Buckley] A newly described species,
Eleocharis occulta, was recently segregated from this taxon (Smith 2001).
var. compressa, COMPRESSED SPIKE-RUSH, FLAT-STEM SPIKE-RUSH. Loamy usually moist soils, often
calcareous conditions. According to S.D. Jones (pers. comm.), var. compressa occurs to the e and n
and apparently does not reach TX; he indicates that TX material identified as var. compressa is
actually var. acutisquamata. Brown and Marcus (1998) also did not find any TX material of E.