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

994 POACEAE/PANICUM
8. Spikelets 1.7–2.2(–2.5) mm long, ca. 1 mm wide, glabrous; leaf blades 3–10 mm wide; plants
of wet habitats ___________________________________________________________ P. verrucosum
8. Spikelets 3–3.6(–4) mm long, ca. 1.5–2 mm wide, conspicuously hispid; leaf blades 1–3 mm
wide; plants of relatively dry habitats ________________________________________ P. brachyanthum
7. Spikelets glabrous or with various pubescence, but not warty.
9. Culms usually swollen and corm-like at very base; leaf sheaths keeled; upper (fertile) floret
finely transversely rugose; spikelets often purplish; species of extreme w margin of East TX
__________________________________________________________________________ P. bulbosum
9. Culms neither swollen nor corm-like at base; leaf sheaths not keeled; upper floret usually
smooth or striate; spikelets variously colored but usually not purplish; including species
widespread in East TX.
10. Culms (at least the lower part) knotty, the conspicuously swollen nodes as much as
twice as thick as the middle of the internodes, almost woody (bamboo-like) in texture,
0.5–3 m tall; rhizomes ca. 1 cm thick, bearing pubescent scale-like leaves ________ P. antidotale
10. Culms not as above; rhizomes absent or less than 0.5 cm thick, bearing glabrous scalelike
leaves.
11. Plants perennial, with long-creeping or short knotty rhizomes; lower floret of each
spikelet staminate.
12. Spikelets usually gaping open at apex; lower glume � 1/2 as long as spikelet;
culms 3–5 mm thick; ligule (1.5–)2–6 mm long ________________________ P. virgatum
12. Spikelets not gaping open at apex or only slightly so (except often gaping
open in Steinchisma hians which was previously included in Panicum); lower
glume � 1/2 as long as spikelet; culms � 3 mm thick; ligule 0.5–2 mm long.
13. Lower glume truncate to rounded to broadly acute, 1 mm or less long;
spikelets 2.2–2.8 mm long; plants with long scaly rhizomes; upper (fertile)
floret widest at or above the middle, rounded apically _________________ P. repens
13. Lower glume abruptly narrowed to an acute apex, 1 mm or more long;
spikelets (2.5–)2.8–3.5 mm long; plants with only short knotty rhizomes;
upper (fertile) floret widest below the middle, narrowed to a minute
apical beak ___________________________________________________ P. coloratum
11. Plants annual or perennial, usually without rhizomes; lower floret of each spikelet
sterile.
14. Lower (first) glume about 1/4–1/3 as long as spikelet, apically truncate to
rounded or broadly acute; leaf sheaths � compressed, usually glabrous or
sparsely pubescent; culms slightly succulent ______________________ P. dichotomiflorum
14. Lower glume 1/3 or more as long as spikelet, apically acute or acuminate;
leaf sheaths rounded, glabrous to with conspicuous pubescence; culms not
succulent.
15. Spikelets 4–6.5 mm long; EITHER spikelets ca. 2–2.5 mm wide OR upper
glume and lemma of lower floret exceeding the fertile floret by 3–4 mm.
16. Spikelets ca. 2–2.5 mm wide, ovoid; upper glume and lemma of lower
floret exceeding the fertile floret by only ca. 1 mm; fertile floret 3–3.8
mm long __________________________________________________ P. miliaceum
16. Spikelets � 1.5 mm wide, lanceolate; upper glume and lemma of lower
floret exceeding the fertile floret by 3–4 mm; fertile floret 1.6–2 mm
long ___________________________________________________ P. capillarioides
15. Spikelets 1–3.7(–4.2) mm long; spikelets much less than 2 mm wide AND
glume and lemma of lower floret not exceeding the fertile floret by 3–4
mm.
17. Spikelets very small, 1–1.4 mm long; leaf blades 2–7 cm long; species
reported in East TX only from Travis Co. __________________________ P. trichoides