Ischaemum rugosum Salisb. Icon.
Stirp. Rar. 1 (1791). Classification. (GPWG 2001) : Subfamily
Panicoideae. Andropogoneae.
Type of Basionym or
Protologue Information: India:
Orissa, ad margines agrorum oryzaceorum, J.G. Koening s.n. (HT: BM).
Key references
(books and floras): [2002] D.Sharp & B.K.Simon, AusGrass, Grasses of
Australia.
Habit. Annual.
Culms decumbent, 10–100 cm tall. Mid-culm nodes glabrous or pubescent. Lateral
branches branched. Ligule an eciliate membrane. Leaf-blades 5–30 cm long, 3–15
mm wide.
Inflorescence.
Inflorescence digitate, a rame, with ramose branches. Rhachis fragile at the
nodes.
Spikelets.
Spikelets sessile, 1 in the cluster. Companion spikelets pedicelled, 1 in the
cluster. Companion spikelets developed or rudimentary, containing empty lemmas
or male, 2–6 mm long. Companion spikelet glumes muticous. Fertile spikelets
2-flowered, the lower floret barren (rarely male), the upper fertile,
comprising 1 basal sterile florets, comprising 1 fertile floret(s), without
rachilla extension, oblong or ovate, dorsally compressed, 4–6 mm long.
Glumes. Glumes
dissimilar, firmer than fertile lemma. Lower glume ovate, membranous or
coriaceous or indurate, much thinner above, keeled, 2-keeled, winged on keel,
winged narrowly, 15 -nerved. Upper glume lanceolate, membranous or chartaceous,
keeled, 1-keeled, 3 -nerved. Upper glume surface glabrous. Florets.
Basal sterile florets 1, male, with palea. Lemma of lower sterile floret 100 %
of length of spikelet, hyaline or membranous.
Fertile lemma 5 mm
long, without keel. Lemma apex lobed, awned, 1 -awned. Median (principal) awn
from a sinus, 15–20 mm long overall, with a twisted column. Grain 2–2.5 mm
long.
Continental
Distribution: Africa, Temperate Asia, Tropical Asia, Australasia, Pacific,
North America, and South America.
Australian
Distribution: Northern Territory, Queensland.
Northern Territory: Darwin &
Gulf. Queensland:
Cook, North Kennedy, South Kennedy.
Notes. Growing
in wet sites in northern N.T. and central and northern coastal Qld. Extends to
most of tropical Asia and introduced to tropical Africa and America.
Infra-specific taxa: var. rugosum, var. segetum .
Pedicelled spikelet
developed I. rugosum var. rugosum
Pedicelled spikelet
much reduced I. rugosum var. setegum
