Hyparrhenia involucrata

HABIT Annual. Butt sheaths glabrous. Culms erect; robust; 100–200 cm long. Culm-nodes glabrous, or bearded. Leaves cauline. Leaf-sheath oral hairs bearded (grey hairs). Ligule a ciliolate membrane; 1–2 mm long. Leaf-blades 20–40 cm long; 4–8 mm wide; flaccid; light green. Leaf-blade surface glabrous, or pilose; hairy abaxially. Leaf-blade margins scabrous.

INFLORESCENCE Synflorescence compound; paniculate; 20–60 cm long. Inflorescence composed of racemes; terminal and axillary; subtended by a spatheole; enclosed. Spatheole lanceolate; 4–7 cm long; scarious; yellow and purple; glabrous. Peduncle 2–3 cm long; glabrous, or pilose above (at base).

Racemes 2; paired; deflexed; 1.5–2.3 cm long; bearing few fertile spikelets; bearing 1–2 fertile spikelets on each. Rhachis fragile at the nodes; ciliate on margins. Rhachis internodes linear. Rhachis internode tip oblique; flat. Raceme-bases flattened; subequal; 1.5 mm long; pubescent.

Spikelets appressed; in pairs. Fertile spikelets sessile; 1 in the cluster. Companion sterile spikelets pedicelled; 1 in the cluster. Pedicels linear; flattened; ciliate; tip oblique.

STERILE SPIKELETS Basal sterile spikelets well-developed; on lower raceme 4 in number; 4 in upper raceme; forming an involucre about the fertile; lanceolate; 7–15 mm long; equalling fertile. Basal sterile spikelet glumes scabrous on margins, or ciliate on margins; lower glume muticous.

Companion sterile spikelets well-developed; containing empty lemmas, or male; lanceolate; dorsally compressed; 7–11 mm long; as long as fertile; separately deciduous. Companion sterile spikelet glumes chartaceous; acute; awned; one glume awned; with 1–20 mm long awn. Companion sterile spikelet lemmas 2; enclosed by glumes.

FERTILE SPIKELETS Spikelets comprising 1 basal sterile florets; 1 fertile florets; without rhachilla extension. Spikelets lanceolate; dorsally compressed; 7–8 mm long; falling entire; deciduous with accessory branch structures. Spikelet callus linear; 2–2.5 mm long; pubescent; base pungent; attached obliquely.

GLUMES Glumes dissimilar; exceeding apex of florets; firmer than fertile lemma. Lower glume lanceolate; 1 length of spikelet; coriaceous; without keels; keel-less except near apex. Lower glume surface glabrous to pubescent. Lower glume apex dentate; 2 -fid. Upper glume linear; coriaceous; without keels.

FLORETS Basal sterile florets barren; without significant palea. Lemma of lower sterile floret lanceolate; 1 length of fertile lemma; hyaline; 2 -veined. Fertile lemma linear; membranous; without keel; 1 -veined. Lemma apex dentate; 2 -fid; awned; 1 -awned. Principal lemma awn from a sinus; geniculate; 70–110 mm long overall; with twisted column. Column of lemma awn hirsute; with 0.5–1 mm long hairs. Palea absent or minute.

FLOWER Lodicules 2; cuneate; fleshy. Anthers 3. Stigmas 2.

FRUIT Caryopsis 3.5 mm long.

DISTRIBUTION Africa: west tropical, west-central tropical, and northeast tropical.

NOTES Andropogoneae. WDC.

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