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

CYPERUS/CYPERACEAE
565
tively more crowded); spikes 10–20(–25) mm
long; culms 2–2.6 mm wide; leaf blades (3–)4–
5.8 mm wide _____________________ C. pseudothyrsiflorus
51. Spikelets usually crowded or extemely densely packed into
short compact spikes, the inflorescence axis usually not easily
visible when pressed.
55. Spikes usually all sessile or nearly so (occasionally 1(–2)
on elongate rays), cylindric, usually more than 2 times as
long as wide __________________________________ C. aggregatus
55. Spikes usually (at least 2 or more) on elongate rays, globose
to ovoid to cylindric, 1–2 times as long as wide.
56. Spikes cylindric or subcylindric, 6–8(–10) mm broad;
spikelets so dense that outline of spike is smooth;
achenes 1.2–1.7 mm long; spikelets 2.2–4(–4.5) mm
long _________________________________________ C. retrorsus
56. Spikes globose to subglobose or ovoid, mostly > 8
mm broad; outline of head appearing somewhat
smooth OR rough; achenes 1.3–2.5 mm long; spikelets
3.5–10(–18) mm long.
57. Spikes globose to subglobose, with (75–)100–
250 spikelets per well-developed spike; spikelets
arranged so densely that outline of spike is �
smooth __________________________________ C. echinatus
57. Spikes globose to subglobose or ovoid, with 10–
50(–70) spikelets per spike; outline of spike appearing
somewhat rough (because of less
densely arranged spikelets).
58. Achenes usually (1.8–)2–2.5 mm long, in
cross section the sides concave; leaf blades
usually 1–3 mm wide; scales of spikelets
usually 3–5 mm long, the terminal scale
involute ______________________ C. retroflexus (in part)
58. Achenes usually 1.3–1.8 mm long, in cross
section the sides ± flat to convex; leaf blades
(at least larger ones) usually 3–4.5 mm wide;
scales of spikelets usually 2.3–3 mm long, the
terminal scale not involute _________________ C. croceus
Cyperus acuminatus Torr. & Hook. ex Torr., (tapering at tip), TAPER-LEAF FLAT SEDGE, TAPER-TIP
FLAT SEDGE. Tufted annual usually 10–40(–45) cm tall; culms slender; leaf sheaths not nodulose;
leaf blades 1–4 mm wide; inflorescences with spikelets digitately arranged in compact heads;
scales weakly S-shaped in longitudinal section, the tip with a slight to marked outward curve;
achenes 0.8–1.1 mm long. Moist areas; nearly throughout TX; throughout much of the U.S.
Mostly May–Oct.
Cyperus aggregatus (Willd.) Endl., (bunched, crowded, in dense clusters), INFLATED-SCALE FLAT
SEDGE. Rhizomatous perennial to 100 cm tall; inflorescences of usually sessile, densely cylindric
spikes; achenes 1.8–2.1 mm long. Roadsides, thickets, dry areas; Newton Co. (E. Keith 603,
SBSC—identified L. Brown); also Bee, Refugio, and San Patricio (TAES) cos. to the s of East TX;
since this species was added after map pages for the flora were completed, no county distribution
map is provided; AZ, LA, MS, NJ, NM, OR, PA, and TX. Jul–Sep. [C. flavus (Vahl) Nees var.
aggregatus (Willd.) Kük.]