Sorghum arundinaceum

HABIT Annual, or perennial. Rhizomes absent. Basal innovations extravaginal. Culms erect; 30–400 cm long; 2–15 mm diam.; without nodal roots, or with prop roots. Culm-internodes hollow. Culm-nodes glabrous, or pubescent. Leaves cauline. Leaf-sheaths narrower than blade at the collar; without keel; smooth; glabrous on surface. Ligule a ciliolate membrane; 2–3 mm long; glabrous on abaxial surface; entire; truncate. Collar glabrous. Leaf-blades 5–75 cm long; 5–70 mm wide. Leaf-blade surface smooth. Leaf-blade margins scabrous; glabrous. Leaf-blade apex acute.

INFLORESCENCE Inflorescence a panicle with branches tipped by a raceme.

Panicle open; linear, or lanceolate, or ovate; 10–60 cm long. Primary panicle branches whorled at most nodes; moderately divided. Panicle branches flexuous; scaberulous; pubescent in axils.

Racemes 0.8–2 cm long; bearing 2–7 fertile spikelets on each. Rhachis fragile at the nodes; ciliate on margins. Rhachis hairs 0.5–1.5 mm long. Rhachis internodes filiform; 2–5 mm long. Rhachis internode tip transverse; cupuliform.

Spikelets appressed; in pairs. Fertile spikelets sessile; 1 in the cluster. Companion sterile spikelets pedicelled; 1 in the cluster. Pedicels filiform; flattened; 0.5 length of fertile spikelet; ciliate.

STERILE SPIKELETS Companion sterile spikelets well-developed; comprising 2 subequal glumes without lemmas, or male; linear to lanceolate; dorsally compressed; 3–8 mm long; shorter than fertile; separately deciduous. Companion sterile spikelet glumes chartaceous; smooth; glabrous; acute; muticous. Companion sterile spikelet lemmas enclosed by glumes.

FERTILE SPIKELETS Spikelets comprising 1 basal sterile florets; 1 fertile florets; without rhachilla extension. Spikelets lanceolate to ovate; dorsally compressed; acute; 4–9 mm long; falling entire; deciduous with accessory branch structures. Spikelet callus base obtuse.

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. Lower glume surface pubescent. Lower glume hairs white, or yellow. Lower glume apex acute. Upper glume ovate; coriaceous; much thinner above; without keels. Upper glume surface pubescent. Upper glume apex acute.

FLORETS Basal sterile florets barren; without significant palea. Lemma of lower sterile floret lanceolate; 0.8 length of spikelet; hyaline; 2 -veined; ciliate on margins; acute. Fertile lemma ovate; dorsally compressed; 1–3 mm long; hyaline; 1 -veined. Lemma margins ciliate. Lemma apex dentate; 2 -fid; muticous, or awned; 1 -awned. Principal lemma awn from a sinus; geniculate; 0–30 mm long overall; with twisted column. Column of lemma awn glabrous. Palea absent or minute.

FLOWER Lodicules 2; oblong; fleshy; ciliate; hairy across the apex. Anthers 3; 2 mm long. Stigmas 2; laterally exserted.

FRUIT Caryopsis with adherent pericarp; oblong; dorsally compressed; 2 mm long. Embryo 0.6 length of caryopsis. Hilum punctiform. Endosperm farinose. Disseminule comprising a rhachis internode.

DISTRIBUTION Africa: north, Macaronesia, west tropical, west-central tropical, northeast tropical, east tropical, southern tropical, south, and western Indian ocean. Asia-tropical: India and Papuasia. Australasia: Australia. Pacific: southwestern, south-central, northwestern, and north-central. North America: southwest USA. South America: Caribbean, western South America, and Brazil.

NOTES Andropogoneae. WDC.

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