Tristachya isalensis

HABIT Perennial; caespitose. Culms erect; 40–70 cm long. Lateral branches lacking, or sparse. Leaf-sheaths glabrous on surface, or pilose; with tubercle-based hairs; outer margin hairy. Ligule a fringe of hairs. Leaf-blades flat, or involute; 1.5–10 cm long; 1.5–2 mm wide. Leaf-blade surface glabrous, or pilose. Leaf-blade margins tuberculate-ciliate. Leaf-blade apex acuminate.

INFLORESCENCE Inflorescence a panicle.

Panicle open; ovate; 3.5–8 cm long; bearing few spikelets. Primary panicle branches 1–4 -nate; not whorled, or whorled at lower nodes; simple, or sparsely divided.

Spikelets in threes. Fertile spikelets pedicelled; 3 in the cluster. Pedicels fused to each other; united wholly; subequal.

FERTILE SPIKELETS Spikelets comprising 1 basal sterile florets; 1 fertile florets; without rhachilla extension. Spikelets lanceolate; laterally compressed; compressed slightly; 9–14 mm long; breaking up at maturity; disarticulating below each fertile floret. Floret callus elongated; 1 mm long; pubescent; pungent.

GLUMES Glumes persistent; exceeding apex of florets. Lower glume lanceolate; 9–14 mm long; 1 length of spikelet; chartaceous; without keels; 3 -veined. Lower glume surface glabrous, or setose; hairy on veins; with tubercle-based hairs. Lower glume apex attenuate. Upper glume lanceolate; 1 length of spikelet; chartaceous; without keels; 3 -veined. Upper glume surface glabrous, or setose; hairy on veins; with tubercle-based hairs. Upper glume apex attenuate.

FLORETS Basal sterile florets male, or barren; with palea; separately deciduous. Lemma of lower sterile floret similar to upper glume; lanceolate; 1 length of spikelet; chartaceous; 5–7 -veined; glabrous, or setose; hairy above; with tubercle-based hairs; acuminate. Fertile lemma oblong; 7–9 mm long; coriaceous; without keel. Lemma surface pubescent; hairy at base; with a transverse row of hair tufts; bearing 6–8 hair tufts in all. Lemma margins involute; interlocking with palea keels. Lemma apex lobed; 2 -fid; with lanceolate lobes; awned; 3 -awned. Principal lemma awn from a sinus; geniculate; subterete below; 12–15 mm long overall; with twisted column; deciduous; abscissing from top of lemma. Lateral lemma awns arising on apex of lobes; 2 mm long. Palea 2 -veined. Palea keels approximate; thickened; winged; narrowly winged. Palea surface pubescent.

FLOWER Anthers 3.

FRUIT Caryopsis with adherent pericarp.

DISTRIBUTION Africa: western Indian ocean.

NOTES Arundinelleae. Gr Madag 1997.

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