Trisetum angustum

HABIT Perennial; caespitose. Culms erect; slender; 12–24 cm long. Culm-nodes constricted. Lateral branches lacking. Leaf-sheaths glabrous on surface, or pilose. Ligule an eciliate membrane; 1.5–2.2 mm long. Leaf-blades flat, or involute; 1–5 cm long; 1 mm wide. Leaf-blade surface glabrous, or puberulous.

INFLORESCENCE Inflorescence a panicle.

Panicle open, or contracted; lanceolate; 4–11 cm long; 1 cm wide. Primary panicle branches appressed; whorled at most nodes. Panicle axis glabrous.

Spikelets appressed; solitary. Fertile spikelets pedicelled.

FERTILE SPIKELETS Spikelets comprising 2–3 fertile florets; with a barren rhachilla extension. Spikelets oblong; laterally compressed; 4.5–6 mm long; breaking up at maturity; disarticulating below each fertile floret. Rhachilla internodes pilose. Floret callus pubescent. Floret callus hairs 0.4–0.6 mm long.

GLUMES Glumes persistent; shorter than spikelet; thinner than fertile lemma. Lower glume ovate; 3–4 mm long; 0.66 length of upper glume; membranous; 1-keeled; 1 -veined. Lower glume lateral veins absent. Lower glume apex acute. Upper glume oblong, or ovate; 4.3–5.8 mm long; 1.1–1.2 length of adjacent fertile lemma; membranous; 1-keeled; 3 -veined. Upper glume apex acute.

FLORETS Fertile lemma elliptic; 4.1–4.8 mm long; membranous; much thinner on margins; keeled; 5 -veined. Lemma surface scaberulous; rough below; pubescent; hairy below. Lemma apex dentate; 4 -fid; muticous, or mucronate. Principal lemma awn subapical. Rhachilla extension pubescent.

FLOWER Anthers 3; 0.8–0.9 mm long. Ovary glabrous.

FRUIT Caryopsis with adherent pericarp; 2.1 mm long. Endosperm farinose.

DISTRIBUTION North America: Mexico. South America: Mesoamericana.

NOTES Aveneae. Fl Meso-Am 1997.

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