Ischaemum rugosum

HABIT Annual. Culms decumbent; 10–100 cm long. Ligule an eciliate membrane. Leaf-blades 5–30 cm long; 3–15 mm wide.

INFLORESCENCE Inflorescence composed of racemes; terminal and axillary.

Racemes 2; paired; appressed back to back; 3–12 cm long. Rhachis fragile at the nodes; angular; ciliate on margins. Rhachis internodes cuneate; 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 cuneate; ciliate.

STERILE SPIKELETS Companion sterile spikelets well-developed, or rudimentary; containing empty lemmas, or male; dorsally compressed; 2–6 mm long; shorter than fertile, or as long as fertile; persistent, or separately deciduous. Companion sterile spikelet glumes chartaceous; muticous. Companion sterile spikelet lemmas 2; enclosed by glumes; muticous.

FERTILE SPIKELETS Spikelets comprising 1 basal sterile florets; 1 fertile florets; without rhachilla extension. Spikelets ovate; dorsally compressed; 4–6 mm long; falling entire; deciduous with accessory branch structures. Spikelet callus base obtuse; inserted.

GLUMES Glumes dissimilar; exceeding apex of florets; firmer than fertile lemma. Lower glume ovate; 1 length of spikelet; coriaceous; much thinner above; 2-keeled; keeled all along; keeled laterally. Lower glume surface convex; rugose; rough below. Upper glume lanceolate; chartaceous; 1-keeled.

FLORETS Basal sterile florets male; with palea. Lemma of lower sterile floret lanceolate; 1 length of spikelet; membranous. Fertile lemma oblong; membranous; without keel. Lemma apex lobed; 2 -fid; awned; 1 -awned. Principal lemma awn from a sinus; geniculate; 15–20 mm long overall; with twisted column. Column of lemma awn glabrous. Palea 1 length of lemma.

DISTRIBUTION Africa: west tropical, east tropical, and western Indian ocean. Asia-temperate: China and eastern Asia. Asia-tropical: India, Indo-China, Malesia, and Papuasia. Australasia: Australia. Pacific: southwestern and northwestern. North America: Mexico. South America: Mesoamericana, Caribbean, northern South America, western South America, and Brazil.

NOTES Andropogoneae. FTEA.

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