Sehima nervosum (Rottler) Stapf
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Common name
Rats's Tail Grass
Whitegrass
Derivation
Sehima Forssk., Fl. Aegypt.-Arab. 178 (1775); from the Eyptian
vernacular name of the type, fide H.T.Clifford, Etymological Dictionary
of Grasses (1996). Named after the Arab sign Saehim, fide
S.D.J.E.Senaratna, The Grasses of Ceylon (1956).
nervosum- from the Latin nervus (nerve) and -osa (abundance). With conspicuous nerves in the glumes or lemmas.
Published in
Fl. Trop. Afr. 9: 36 (1917).
Habit
Perennial, tufted. Culms erect, 30100 cm tall, wiry. Mid-culm nodes glabrous
or bearded. Ligule a fringe of hairs, 12 mm long. Leaf-blades 540
cm long, 27 mm wide, glaucous. Leaf-blade apex attenuate, filiform.
Inflorescence
Rames single, straight or arcuate, 312 cm long. Rhachis fragile at the
nodes, flattened, ciliate on margins. Rame internodes cuneate, 3.54 mm
long. Rame internode tip oblique, crateriform.
Spikelets
Spikelets squeezed between internode and pedicel, in pairs, one sessile and
fertile and the other (companion) spikelet pedicelled. Pedicels cuneate, flattened,
3.54 mm long, ciliate on margins, tip rectangular. Companion spikelets
developed, male, containing empty lemmas or male, lanceolate or elliptic, dorsally
compressed, 610 mm long, as long as fertile, separately deciduous. Companion
spikelet glumes coriaceous, distinctly nerved, 57-nerved, ciliate on margins,
acute, muticous. Companion spikelet lemmas 2, enclosed by glumes, muticous.
Fertile spikelets 2-flowered, comprising 1 fertile floret, lower floret male,
upper fertile, without rhachilla extension, elliptic, laterally compressed,
610 mm long, falling entire, deciduous with accessory branch structures.
Spikelet callus square, pilose, base obtuse, inserted.
Glumes
Glumes dissimilar, firmer than fertile lemma. Lower glume elliptic, asymmetrical,
100% of length of spikelet, cartilaginous or coriaceous, much thinner above,
2-keeled, keeled dorsally below, flaring to lateral above, wingless or winged
on keel, winged narrowly, winged near apex, 6-nerved. Lower glume lateral nerves
branching above. Lower glume intercarinal nerves absent below, prominent above.
Lower glume surface deeply depressed. Lower glume surface glabrous. Lower glume
apex dentate, 2-fid, mucronate. Upper glume elliptic, 6 mm long, membranous
or chartaceous, 1-keeled, winged on keel, winged near apex, 35-nerved.
Upper glume surface scabrous, rough on nerves. Upper glume margins ciliate.
Upper glume apex acute, awned. Upper glume awn 916 mm long.
Florets
Basal sterile floret 1, with palea. Lemma of lower sterile floret oblong, 6
mm long, hyaline, 2-nerved, ciliate on margins. Palea of lower sterile floret
hyaline. Fertile lemma lanceolate, 5 mm long, hyaline, 3-nerved. Lemma margins
ciliate. Lemma apex lobed, 2-fid, with linear lobes, incised 30% of lemma
length, 1-awned. Median (principal) awn from a sinus, geniculate, 2040
mm long overall, with a twisted column. Column hispidulous, hairy on the spiral.
Palea 5 mm long, 100% of length of lemma, hyaline, without keels. Anthers
3 mm long.
Continental Distribution:
Africa, Temperate Asia, Tropical Asia, Australasia.
Australian Distribution:
Western Australia, Northern Territory, Queensland, New South Wales.
Western Australia: Gardner, Fitzgerald, Hall, Dampier. Northern Territory: Darwin & Gulf, Victoria River, Barkly Tableland, Central Australia North. Queensland: Cook, Burke, North Kennedy, South Kennedy, Port Curtis, Leichhardt, Burnett, Wide Bay, Darling Downs, Moreton, Gregory North, Mitchell, Maranoa. New South Wales: North-Western Slopes.
Classification. (GPWG
2001):
Panicoideae: Andropogoneae
Notes
Native. Common in savanna country througout subtropical and tropical Australia
in Qld, northern N.S.W., N.T. and W.A. Extends through New Guinea and SE Asia
to India and tropical Africa. Poor quality fodder. Flowers all year.
Habit (photo)
© E.Anderson
Inflorescence (line drawing)
© Queensland Herbarium
by D. Sharp
Courtesy of the Toowoomba Field Naturalist Club