Rottboellia cochinchinensis

HABIT Annual. Culms erect; 30–300 cm long; with prop roots. Lateral branches ample. Leaves cauline. Leaf-sheaths as wide as blade at the collar; hispid; with tubercle-based hairs. Ligule a ciliolate membrane; 1 mm long; truncate. Leaf-blades 15–45 cm long; 5–20 mm wide. Leaf-blade surface scaberulous. Leaf-blade apex acuminate.

INFLORESCENCE Inflorescence composed of racemes; terminal and axillary; subtended by an inflated leaf-sheath; exserted, or embraced at base by subtending leaf. Peduncle antrorsely scabrous above; widened at apex.

Racemes 1; single; erect; smoothly terete; unilateral; 3–15 cm long. Rhachis fragile at the nodes; subcylindrical and excavated; 2–3.5 mm wide; glabrous on margins; terminating in a sterile spikelet. Spikelet packing abaxial; regular. Rhachis internodes oblong; 5–7 mm long. Rhachis internode tip transverse; crateriform; with simple rim.

Spikelets sunken; in pairs. Fertile spikelets sessile; 1 in the cluster. Companion sterile spikelets pedicelled; 1 in the cluster. Pedicels fused to internode; united wholly; oblong; flattened; 1 length of fertile spikelet (shorter than internode).

STERILE SPIKELETS Companion sterile spikelets well-developed; containing empty lemmas; ovate; dorsally compressed; 3–5 mm long; deciduous with the fertile. Companion sterile spikelet glumes indurate; winged on margins; distinctly veined; smooth; glabrous; obtuse; muticous. Companion sterile spikelet lemmas enclosed by glumes.

Apical sterile spikelets barren; 4–14 in number.

FERTILE SPIKELETS Spikelets comprising 1 basal sterile florets; 1 fertile florets; without rhachilla extension. Spikelets ovate; dorsally compressed; gibbous; 3.5–5 mm long; falling entire; deciduous with accessory branch structures. Spikelet callus glabrous; base truncate; with central peg; attached transversely.

GLUMES Glumes dissimilar; with lower wider than upper; reaching apex of florets; firmer than fertile lemma. Lower glume ovate; 1 length of spikelet; indurate; 2-keeled; winged on keel; winged near apex; 13 -veined. Lower glume apex emarginate. Upper glume ovate; gibbous; 1 length of adjacent fertile lemma; chartaceous; 1-keeled; winged on keel; winged all along; 11 -veined. Upper glume apex acute.

FLORETS Basal sterile florets male; with palea. Lemma of lower sterile floret ovate; 1 length of fertile lemma; hyaline; 5 -veined; acute. Palea of lower sterile floret membranous. Fertile lemma oblate; laterally compressed; gibbous; 2.5–4.5 mm long; hyaline; keeled; lightly keeled; keeled below; 1 -veined. Lemma apex acute. Palea elliptic; 1 length of lemma; hyaline; 0 -veined; without keels. Palea apex acute.

FLOWER Lodicules 2; oblong; 2 mm long; fleshy. Anthers 3; 2 mm long. Stigmas 2.

FRUIT Caryopsis with tardily free pericarp; ovoid; 3.5 mm long; pallid. Embryo 0.5 length of caryopsis. Hilum punctiform. Endosperm farinose. Disseminule comprising a rhachis internode.

DISTRIBUTION Africa: Macaronesia, west tropical, west-central tropical, northeast tropical, east tropical, southern tropical, south, and western Indian ocean. Asia-temperate: Arabia, China, and eastern Asia. Asia-tropical: India, Indo-China, Malesia, and Papuasia. Australasia: Australia. North America: southeast USA and Mexico. South America: Mesoamericana, Caribbean, northern South America, western South America, Brazil, and southern South America.

NOTES Andropogoneae. WDC.

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