Sorghum macrospermum

HABIT Annual. Culms erect; robust; 180–380 cm long; 5–10 mm diam.; without nodal roots, or with prop roots. Culm-nodes glabrous, or pubescent. Leaves cauline. Ligule a ciliolate membrane; 2.6–5 mm long. Leaf-blade base broadly rounded. Leaf-blades 30–60 cm long; 15–30 mm wide. Leaf-blade surface glabrous, or pilose; hairy adaxially; with tubercle-based hairs. Leaf-blade margins smooth, or spinulose. Leaf-blade apex acuminate.

INFLORESCENCE Inflorescence a panicle with branches tipped by a raceme.

Panicle open; ovate; effuse; 15–35 cm long. Primary panicle branches drooping, or reflexed; distant; 1–4 -nate; not whorled; simple, or moderately divided; 4–8 cm long. Panicle branches glabrous in axils, or pubescent in axils.

Racemes 4–12 cm long; bearing 9–21 fertile spikelets on each. Rhachis fragile at the nodes; ciliate on margins. Rhachis internodes linear; 4–6 mm long. Rhachis internode tip transverse; cupuliform.

Spikelets in pairs. Fertile spikelets sessile; 1 in the cluster. Companion sterile spikelets pedicelled; 1 in the cluster. Pedicels filiform; 5–6 mm long; ciliate.

STERILE SPIKELETS Basal sterile spikelets absent, or well-developed; 0–4 in number.

Companion sterile spikelets well-developed; comprising 2 subequal glumes without lemmas; linear; 6.5–13.5 mm long; as long as fertile; separately deciduous. Companion sterile spikelet glumes chartaceous; 7–17 -veined; glabrous, or pubescent; muticous.

FERTILE SPIKELETS Spikelets comprising 1 basal sterile florets; 1 fertile florets; without rhachilla extension. Spikelets lanceolate; dorsally compressed; 10–11 mm long; falling entire; deciduous with accessory branch structures. Spikelet callus 0.2 mm long; bearded; base truncate, or obtuse. Spikelet callus hairs 0.1–0.25 length of spikelet.

GLUMES Glumes dissimilar; with lower wider than upper; exceeding apex of florets; firmer than fertile lemma; shiny. Lower glume ovate; 1 length of spikelet; coriaceous; much thinner above; without keels; keel-less except near apex; 15–20 -veined. Lower glume surface scabrous (above); glabrous. Lower glume apex dentate; 2 -fid. Upper glume ovate; coriaceous; much thinner above; without keels; winged on margins; 7 -veined. Upper glume lateral veins with cross-veins. Upper glume surface scabrous; rough above; pubescent. Upper glume margins ciliate. Upper glume apex truncate, or obtuse.

FLORETS Basal sterile florets barren; without significant palea. Lemma of lower sterile floret elliptic; 0.8 length of spikelet; hyaline; 2 -veined; ciliolate on margins. Fertile lemma oblong; 3.5–4 mm long; hyaline; 1 -veined. Lemma margins ciliate. Lemma apex dentate; 2 -fid; awned; 1 -awned. Principal lemma awn from a sinus; geniculate; 33–52 mm long overall; with twisted column. Column of lemma awn pubescent; hairy on the spiral. Palea absent or minute.

FLOWER Lodicules 2; glabrous. Anthers 3; 5.5–6.8 mm long.

FRUIT Caryopsis with adherent pericarp; ellipsoid, or ovoid; 5.2–6.3 mm long.

DISTRIBUTION Australasia: Australia.

NOTES Andropogoneae. Lazarides.

Please cite this publication as detailed in How to Cite Version: 3rd February 2016.