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

1008 POACEAE/PASPALUM
PASPALUM L. CROWN GRASS, BEAD GRASS
Primarily perennials (P. boscianum, P. convexum, P. repens, and P. scorbiculatum are annuals);
ligule a membrane; inflorescence a panicle with a central axis and (1–)2–many spike-like
branches; spikelets solitary or in pairs, subsessile or short-pedicelled, in 2–4 rows on one side
(abaxial) of each flattened, sometimes winged branch, lanceolate to nearly circular in outline,
flattened on one face, 2-flowered, the lower floret sterile or staminate, the upper floret perfect,
the spikelets oriented so that the rounded back of the lemma of the fertile floret is facing the
axis of the inflorescence branch; disarticulation below the glumes; lower glume usually absent
or reduced; upper glume and lemma of sterile floret similar to each other; lemma of fertile floret
usually firm or hardened, typically smooth and shiny, with firm inrolled margins.
AA C4 genus of 300–400 species (Allen & Hall 2003), principally of tropical and warm areas
of the Americas, with a few species in the Old World (Morrone et al. 1996). Morrone et al. (1996)
reported ca. 330 species. Some are characteristic of the pampas; P. pyramidale Nees grows to 15
m tall in the Amazon. A number of species are variously used for fodder, as pasture species, or
as a grain crop (P. scrobiculatum L.—KODO-MILLET in India), while others are considered significant
weeds (Watson & Dallwitz 1992). � Ergot fungi, Claviceps purpurea (Fr.: Fr.) Tul., C.
paspali F. Stevens & J.G. Hall and related species, are known to grow on a number of TX grasses
including P. dilatatum and other Paspalum species. These fungi, whose overwintering structures
(= sclerotia) replace some grains in the grass inflorescence, often produce toxic alkaloids
(e.g., ergocryptine and ergotamine) chemically similar to LSD. Cattle who consume infected
plants can become hyperexcitable, have convulsions or tremors, develop staggers syndrome
(“paspalum staggers”) or gangrene, or die; significant livestock losses have occurred. Humans
can also be affected (see discussion under the genus Secale) (Sperry et al. 1955; Kingsbury 1964,
1965; Burrows & Tyrl 2001; Hart et al. 2001). (Probably from the Greek paspalos, millet or meal)
(subfamily Panicoideae, tribe Paniceae)
REFERENCES: Chase 1929; Silveus 1942; Banks 1966; Allred 1982; Brummitt 1983; de Wet et al.
1983a; Crins 1991; Pohl & Davidse 1994b; Cialdella et al. 1995; Morrone et al. 1995, 1996, 2000;
Rua 1996; Allen & Hall 2003; Zuloaga et al. 2004.
1. Inflorescence branches with axis broadly winged, sometimes almost leaf-like, nearly as wide or
wider than the rows of spikelets, the wing margins sometimes even slightly wrapping around
the spikelets.
2. Axis of inflorescence branch extending beyond the most distal spikelet in form of a pointed
tip; inflorescence branches usually numerous (8–65+), eventually falling from the main axis;
spikelets 1.2–1.7(–2) mm long ______________________________________________________ P. repens
2. Axis of inflorescence branch not extending beyond the most distal spikelet; inflorescence
branches usually 2–12(–15), not falling from the main axis; spikelets 1.7–4 mm long.
3. Spikelets 3.2–4 mm long, not in pairs (with neither aborted spikelet nor pedicel present
immediately beside or below fertile spikelet); species rare in East TX _________________ P. acuminatum
3. Spikelets 1.7–3.6 mm long, in pairs or with aborted remnant spikelet or pedicel beside or
below fertile spikelet (except not in pairs in P. dissectum which has spikelets 2.3 mm or less
long); including species widespread and common in East TX.
4. Spikelets 1.7–2.1(–2.3) mm long, in 2 rows on the branch axis, not in pairs (with neither
aborted spikelet nor pedicel present immediately beside or below fertile spikelet) _____ P. dissectum
4. Spikelets 2–3.6 mm long, usually in 4 or less frequently 2 rows on the branch axis, in
pairs or with aborted remnant spikelet or pedicel beside or below fertile spikelet.
5. Spikelets pubescent.
6. Leaf blades flat, (4–)6–18 mm wide, the margins often crisped; spikelets 1.5–2 mm
wide ______________________________________________________________ P. pubiflorum
6. Leaf blades often folded or involute, usually 2–6 mm wide, the margins not crisped;
spikelets ca. 1.5 mm or less wide _____________________________________ P. har twegianum