GrassBase - The Online World Grass Flora


W.D. Clayton, M. Vorontsova, K.T. Harman & H. Williamson

© Copyright The Board of Trustees, Royal Botanic Gardens, Kew.

Trisetum ambiguum

HABIT Perennial; caespitose. Rhizomes elongated. Basal innovations extravaginal. Culms 17–34 cm long. Leaf-sheaths longer than adjacent culm internode; pubescent. Ligule a ciliolate membrane; 1.5–2.5 mm long. Leaf-blades flat, or convolute; 1.5–7 cm long; 2–3 mm wide. Leaf-blade surface scabrous; rough adaxially. Leaf-blade apex abruptly acute; hooded.

INFLORESCENCE Inflorescence a panicle. Peduncle pubescent above, or pilose above.

Panicle spiciform; linear; continuous; 4.5–7.5 cm long; 1.5 cm wide. Panicle axis pubescent.

Spikelets solitary. Fertile spikelets pedicelled. Pedicels pubescent.

FERTILE SPIKELETS Spikelets comprising 1(–2) fertile florets; with a barren rhachilla extension. Spikelets oblong; laterally compressed; 6.8–8 mm long; breaking up at maturity; disarticulating below each fertile floret. Floret callus pubescent. Floret callus hairs 0.5–0.8 mm long.

GLUMES Glumes persistent; similar; with lower narrower than upper; exceeding apex of florets; thinner than fertile lemma; gaping. Lower glume lanceolate; 6–7.5 mm long; 1 length of upper glume; membranous; 1-keeled; 1 -veined. Lower glume primary vein scaberulous. Lower glume lateral veins absent. Lower glume apex acuminate. Upper glume lanceolate; 6.8–8 mm long; 1.3 length of adjacent fertile lemma; membranous; 1-keeled; 1(–3) -veined. Upper glume primary vein scabrous. Upper glume lateral veins absent, or obscure. Upper glume apex acuminate.

FLORETS Fertile lemma oblong; 4–6 mm long; membranous; keeled; 5 -veined. Lemma lateral veins excurrent. Lemma surface scabrous. Lemma apex dentate; 4 -fid; awned; 1 -awned. Principal lemma awn dorsal; arising 0.5 way up back of lemma; geniculate; 5–7.5 mm long overall; with twisted column. Palea gaping; 3.6–4.5 mm long; hyaline. Palea keels scaberulous. Rhachilla extension 2.5 mm long; pubescent.

FLOWER Lodicules 2; 0.6–0.7 mm long. Anthers 3; 0.6–0.8 mm long.

FRUIT Caryopsis with adherent pericarp; fusiform; 3.4 mm long; hairy at apex; apex rostrate. Hilum elliptic. Endosperm liquid.

DISTRIBUTION South America: southern South America.

NOTES Aveneae. Rug & Nic 1997.

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