Tripsacum australe

HABIT Perennial; caespitose. Culms erect, or geniculately ascending; robust; 200–350 cm long; 10–15 mm diam. Culm-internodes distally glabrous. Culm-nodes purple. Leaves basal and cauline. Leaf-sheaths keeled; woolly. Ligule a ciliolate membrane; 0.4–0.6 mm long. Leaf-blade base with a false petiole. Leaf-blades lanceolate; 30–140 cm long; 18–40 mm wide. Leaf-blade surface glabrous. Leaf-blade apex acuminate.

INFLORESCENCE Monoecious; with male and female spikelets in the same inflorescence. Inflorescence composed of racemes; terminal and axillary.

Racemes 1–4; single, or paired, or digitate; erect; smoothly terete; unilateral; 17–22 cm long. Rhachis female portion 5.5–7.5cm long, fragile at the nodes; subcylindrical and excavated; 3.4–5 mm wide; glabrous on surface. Spikelet packing abaxial. Rhachis internodes oblong; adherent to upper glume of sessile spikelet. Rhachis internode tip transverse; crateriform.

Sexes segregated; on bisexual branches; with male above. Spikelets sunken; solitary. Fertile spikelets sessile. Male spikelets sessile, or sessile and pedicelled; 2 in a cluster. Pedicels (male) 0–0.7 mm long.

FERTILE SPIKELETS Spikelets comprising 1 basal sterile florets; 1 fertile florets; without rhachilla extension. Spikelets ovate; dorsally compressed; 5.5–7 mm long; falling entire; deciduous with accessory branch structures. Spikelet callus base truncate; with central peg; attached transversely.

GLUMES Glumes dissimilar; reaching apex of florets; firmer than fertile lemma. Lower glume ovate; 1 length of spikelet; indurate; without keels. Lower glume apex acuminate. Upper glume ovate; cartilaginous; without keels. Upper glume apex acute.

FLORETS Basal sterile florets barren; without significant palea. Lemma of lower sterile floret oblong; hyaline. Fertile florets female. Fertile lemma oblong; hyaline; without keel. Palea hyaline.

FLOWER Anthers 3; 3.2–3.5 mm long. Styles connate below.

MALE Male spikelets distinct from female; with free pedicels; all deciduous together; lanceolate, or elliptic; 7–8.5 mm long; hairy; obtuse, or acute. Male spikelet glumes 2; coriaceous; muticous. Male spikelet lemma 6–8 mm long; 5 -veined.

DISTRIBUTION North America: Mexico. South America: Caribbean, northern South America, western South America, Brazil, and southern South America.

NOTES Andropogoneae. Fl Guiana 1997.

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