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

588 CYPERACEAE/ELEOCHARIS
16. Tubercle well-differentiated from achene, the junction with achene clearly
visible; achenes 0.5–0.8(–0.9) mm long.
17. Achenes finely reticulate (use dissecting scope); tubercle > 1/3 length
of achene; distal leaf sheath apex with a reddish marginal band ________ E. vivipara
17. Achenes smooth; tubercle � 1/3 length of achene; distal leaf sheath
apex without a reddish marginal band.
18. Tubercle covering most of summit of achene; achenes often broadest
� at or near the middle; spikelets with lowermost scale similar
to other scales ____________________________________________ E. minima
18. Tubercle tiny, perched on summit of achene and not covering most
of it; achenes broadest above the middle; spikelets with lowermost
scale different from other scales, usually longer and often
resembling an involucral bract.
19. Lowermost scale of spikelet (= scale at base of spikelet) with
apex subacute to acute or with the midvein excurrent ______ E. microcarpa
19. Lowermost scale of spikelets with apex rounded _____________ E. brittonii
14. Achenes biconvex in cross section (= convex on both sides, � lens-shaped), variously
colored, including dark reddish black to black at maturity; styles usually 2branched.
20. Distal leaf sheaths with apex inflated, loose, often conspicuously wrinkled, frequently
disintegrating, usually not purplish red at base; plants perennial, delicately
rhizomatous and mat-forming; spikelets ellipsoid ___________________ E. flavescens
20. Distal leaf sheaths with apex tightly sheathing, neither wrinkled nor disintegrating,
sometimes purplish red at base; plants annual, tufted, not rhizomatous;
spikelets ellipsoid to ovoid to nearly orbicular.
21. Spikelets ellipsoid to lance-ovoid; achenes 0.3–0.6 mm long; perianth
bristles white to nearly colorless; culms 2–15(–25) cm tall ____________ E. atropurpurea
21. Spikelets ovoid to nearly orbicular; achenes 0.5–1.1 mm long; perianth
bristles usually red-brown (rarely whitish); culms 4–45 cm tall __________ E. geniculata
8. Spikelets usually larger, 1.8–5 mm thick in flower, 3–25 mm or more long; culms coarsely threadlike,
wiry, or thickened, to 2 mm wide.
22. Achenes biconvex in cross section (= convex on both sides, � lens-shaped); styles usually
2-branched; stigmas usually 2.
23. Plants annuals with only fleshy-fibrous roots, pulled up easily.
24. Scales of spikelets definitely acute (= pointed); spikelets narrowly lanceoloid, acute
to acuminate _______________________________________________________ E. lanceolata
24. Scales of spikelets obtuse; spikelets lanceoloid to broadly ovoid to oblong-ovoid
or nearly orbicular, obtuse to acute.
25. Tubercle much narrower than summit of achene, 0.1–0.2 mm wide, somewhat
constricted basally and thus slightly separated from achene, lightcolored
________________________________________________________ E. geniculata
25. Tubercle nearly as wide as summit of achene, 0.5–1 mm wide, in outline merging
with achene, dark-colored.
26. Spikelets broadly ovoid to oblong-ovoid and obtuse, mostly 3–12 mm
long; bristles mostly surpassing the tubercle; tubercle 1/3–nearly 1/2
as high as achene, 0.35–0.5 mm long _________________________________ E. obtusa
26. Spikelets mostly lanceoloid and acute, usually 5–18(–20) mm long; bristles
shorter than to barely reaching tip of tubercle; tubercle short, not more
than 1/4 as high as achene, 0.1–0.3 mm long _____________________ E. engelmannii
23. Plants perennials with rhizomes, often very difficult to pull up (and underground parts
often lost), the rhizomes sometimes purplish red.