Acrachne racemosa (B.Heyne ex Roem. & Schult.) Ohwi |
Derivation
Acrachne Wright & Arn. ex Chiov., Annuario Reale Ist. Bot. Roma
8: 361 (1907); from the Greek akra (the terminal point) and achne
(a scale), referring to the fine-pointed glumes and lemmas.
racemosa- from the Latin racemus (stalk of a cluster of grapes)
and -osa (abundance). The spikelets are borne in racemes or contracted
panicles.
Published in
Bull. Tokyo Sci. Mus.18: 1 (1947).
Common synonyms
Acrachne verticillata (Roxb.) Chiov.
Habit
Annual, tufted. Basal leaf sheaths glabrous. Young shoots intravaginal. Culms
geniculately ascending or decumbent, 15100 cm tall, 13 mm diam.,
26-noded. Lateral branches sparsely branched. Leaves cauline. Leaf-sheaths
as wide as blade at the collar. Ligule a fringed membrane, 0.51.3 mm long.
Leaf-blades flat, 1375 cm long, 312 mm wide. Leaf-blade surface
smooth, glabrous or pilose. Leaf-blade margins cartilaginous. Leaf-blade apex
attenuate, filiform.
Inflorescence
Inflorescence subdigitate, a panicle of racemes, with racemose branches. Racemes
225, in several whorls, unilateral, 1.510 cm long. Central inflorescence
axis 015 cm long. Rhachis angular, terminating in a sterile spikelet.
Spikelet packing broadside to rhachis, regular.
Spikelets
Spikelets appressed, solitary. Apical sterile spikelets rudimentary, 1 in number.
Fertile spikelets many flowered, comprising 625 fertile florets, with
diminished florets at the apex, oblong, laterally compressed, 513 mm long,
2.53 mm wide, breaking up at maturity. Spikelets rhachilla persistent.
Spikelets retaining paleas, tough throughout or fragile above, with the distal
florets falling as a whole. Rhachilla internodes 0.1 mm long, eventually visible
between lemmas.
Glumes
Glumes deciduous, similar. Lower glume linear or lanceolate or elliptic or oblong,
1.22.9 mm long, 5080% length of upper glume, membranous or cartilaginous,
1-keeled, 1-nerved. Lower glume lateral nerves absent. Lower glume apex acuminate,
mucronate. Upper glume ovate, 1.53 mm long, 5070% of length
of adjacent fertile lemma, membranous, 1-keeled, 1-nerved, midnerve scabrous.
Upper glume lateral nerves absent. Upper glume apex entire, acuminate, mucronate.
Florets
Fertile florets recurved at tip. Fertile lemma lanceolate or elliptic or oblong
or ovate, laterally compressed, ovate in profile, 23 mm long, membranous
or cartilaginous, yellow to mid-green, 3-nerved. Lemma midnerve scaberulous.
Lemma lateral nerves excurrent. Lemma surface glabrous. Lemma apex entire, acute,
1-awned. Median (principal) awn 0.30.9 mm long overall. Palea lanceolate
or ovate, bowed outwards, 80% of length of lemma, 2-nerved. Palea keels
scabrous. Palea apex dentate, 2-fid, acute. Apical sterile florets resembling
fertile though underdeveloped. Lodicules 2, cuneate, fleshy. Anthers 3, 0.4
mm long. Stigmas 2, protandrous, laterally exserted. Grain with free soft pericarp,
ellipsoid or oblong, terete, biconvex, estipitate, grooved, 0.81.1 mm
long, rugose, apex unappendaged. Embryo 40% of length of grain. Hilum punctiform.
Endosperm farinose.
Continental Distribution:
Africa, Temperate Asia, Tropical Asia, Australasia.
Australian Distribution:
Western Australia, Northern Territory, Queensland.
Western Australia: Fortescue, Austin. Northern Territory: Darwin & Gulf, Victoria River, Barkly Tableland. Queensland: Burke, North Kennedy, South Kennedy, Leichhardt.
Classification. (GPWG
2001):
Chloridoideae: Cynodonteae
Notes
Recorded from the Pilbara and Kimberley Regions of W.A., the Darwin area and
Barkly Tableland of the N.T., and central eastern Qld; pan-tropical. Occurs
in brown, sandy loam over loamy clay on coastal flats in association with low,
deciduous, vine thickets in the Kimberley Region of W.A.; otherwise in monsoonal
areas usually along creeklines on sandy or skeletal soils, with Eucalyptus,
Acacia or Atalaya species
Inflorescence (scanned specimen)
© Queensland Herbarium
by Will Smith