Ischaemum tropicum

HABIT Perennial; caespitose. Rhizomes short. Culms erect; 80–120 cm long. Culm-nodes pubescent. Lateral branches lacking. Ligule a fringe of hairs; 2 mm long. Leaf-blades 8–20 cm long; 2–4 mm wide. Leaf-blade surface glabrous.

INFLORESCENCE Inflorescence composed of racemes.

Racemes 2–3; paired, or digitate; 4–6 cm long; bearing 8–14 fertile spikelets on each. Rhachis fragile at the nodes; angular; ciliate on margins. Rhachis internodes oblong; 4.5 mm long; flat and forming a U or V shape with the pedicel in rear view. Rhachis internode tip transverse; cupuliform.

Spikelets in pairs. Fertile spikelets sessile; 1 in the cluster. Companion sterile spikelets pedicelled; 1 in the cluster. Pedicels oblong; 4 mm long; 0.75–0.8 length of fertile spikelet; ciliate.

STERILE SPIKELETS Companion sterile spikelets represented by single glumes, or rudimentary, or well-developed; comprising 2 subequal glumes without lemmas, or containing empty lemmas; elliptic; 2–7 mm long; shorter than fertile, or as long as fertile, or longer than fertile; separately deciduous. Companion sterile spikelet glumes coriaceous; keeled; 11 -veined; glabrous; muticous. Companion sterile spikelet lemmas 1-awned.

FERTILE SPIKELETS Spikelets comprising 1 basal sterile florets; 1 fertile florets; without rhachilla extension. Spikelets elliptic; dorsally compressed; 5–5.5 mm long; 1.5–2 mm wide; falling entire; deciduous with accessory branch structures. Spikelet callus oblong; base truncate; inserted.

GLUMES Glumes dissimilar; exceeding apex of florets; firmer than fertile lemma. Lower glume elliptic; 1 length of spikelet; chartaceous; 2-keeled; keeled above; keeled laterally; winged on keel; winged narrowly; winged above; 10 -veined. Lower glume surface convex; glabrous. Lower glume apex dentate; 2 -fid. Upper glume lanceolate; coriaceous; 1-keeled; 4 -veined. Upper glume surface glabrous. Upper glume apex acuminate; awned; 1 -awned. Upper glume awn 2 mm long.

FLORETS Basal sterile florets male; with palea. Lemma of lower sterile floret lanceolate; 6 mm long; membranous; acute. Fertile lemma oblong; 5 mm long; membranous; without keel. Lemma apex lobed; 2 -fid; incised 0.33 of lemma length; awned; 1 -awned. Principal lemma awn from a sinus; geniculate; 12–16 mm long overall; with twisted column. Column of lemma awn glabrous. Palea 5 mm long.

FLOWER Anthers 3; 2.5 mm long.

DISTRIBUTION Australasia: Australia.

NOTES Andropogoneae. Simon 1994.

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