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

806 POACEAE
KEY F
Spikelets in pairs (1 sessile or nearly so and 1 pedicelled, both sometimes pedicelled,
especially at branch tips), the pedicelled spikelet similar to sessile spikelet or usually reduced
(in some cases to only a bristle) or sometimes absent (often represented by an empty pedicel);
fertile spikelets with 1 perfect floret; glumes thicker than lemmas of fertile florets, often
subequal; pedicels often flattened and with long-ciliate margins
1. Spikelets sessile and apparently solitary, the pedicellate spikelet absent (actually so reduced as
to be represented only by a pedicel).
2. Inflorescence a solitary, terminal, spike-like raceme ca. 2–6 cm long and ca. 1.5–2.5 mm wide
(pencil-like but much smaller in diam.) _____________________________________________ Eremochloa
2. Inflorescence of 2–several digitately arranged branches OR a panicle.
3. Leaf blades cordate-clasping at base; plants low annuals creeping and rooting at lower
nodes ______________________________________________________________________ Arthraxon
3. Leaf blades not cordate-clasping at base; plants usually erect perennials or annuals.
4. Inflorescences both terminal and axillary, of digitate clusters of 2–5 branches (the clusters
sometimes clustered); peduncles each subtended by, and often partly enclosed by,
a sometimes sheathing bract _______________________________________________ Andropogon
4. Inflorescence terminal only, a long-exserted and elongate panicle of numerous branches;
peduncles not subtended by a bract _________________________________________ Sorghastrum
1. Spikelets in pairs, the pedicelled spikelet similar to sessile or shorter-pedicelled spikelet OR reduced,
but usually not so reduced as to be represented by a pedicel only.
5. Inflorescence a solitary (1 per peduncle), straight, elongate, very narrow, spike-like raceme
(due to the pedicels being closely appressed to branch axis); sessile spikelets awnless or awned.
6. Awns absent.
7. Infloresence axis pilose; sessile spikelet 6–8 mm long; pedicelled spikelet similar in size
to sessile one; plant tufted, not mat-forming, with erect culms 60–100(–120) cm tall ______ Elionurus
7. Inflorescence axis glabrous; sessile spikelet 3–4 mm long; pedicelled spikelet usually
much reduced; plant mat-forming, the culms 35 cm or less tall _____________________ Eremochloa
6. Awns present on some spikelets, the awns 4–12(–15) cm long.
8. Awned spikelet sessile; glumes and awn of awned spikelet dark brown at maturity; inflorescence
axis disarticulating at maturity ____________________________________ Heteropogon
8. Awned spikelet short-pedicelled; glumes and awn of awned spikelet light-colored at
maturity; inflorescence axis remaining intact at maturity _________________________ Trachypogon
5. Inflorescence not as above, often branched, and usually not narrowly elongate and spike-like
(but sometimes a narrowly cylindrical panicle); sessile spikelets usually awned.
9. Sessile (or nearly so) and pedicellate spikelets both fertile, alike morphologically.
10. Plants annual; culms creeping at base and rooting at the lower nodes; inflorescences
of (1–)2–5(–6) usually subdigitately arranged spike-like racemes; spikelets without a
conspicuous tuft of long hairs at base (= without callus hairs) ___________________ Microstegium
10. Plants perennial; culms neither creeping nor rooting at the nodes; inflorescences
panicles, either large and with numerous branches terminating in numerous racemes
OR narrowly cylindrical; spikelets often, but not always, with a conspicuous tuft of long
callus hairs (= whorl of hairs attached directly below spikelet).
11. Spikelets in pairs of 1 sessile, 1 pedicelled; inflorescence branches disarticulating
(breaking into sections) at maturity, the pedicels falling with the sessile spikelets
____________________________________________________________________ Saccharum
11. Spikelets in pairs of 1 long-pedicelled, 1 short-pedicelled; pedicels 1–6 mm long; inflorescence
branches not disarticulating, the spikelets falling from pedicels at maturity.
12. Lemma with awn 5–12 mm long; inflorescence branches 8–15(–30) cm long
________________________________________________________________ Miscanthus