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.

Aristida laxa

HABIT Perennial; caespitose; clumped densely. Butt sheaths persistent and investing base of culm; with curly dead sheaths. Culms 50–100 cm long; 1–1.5 mm diam. Culm-internodes solid; distally glabrous. Culm-nodes glabrous. Lateral branches lacking. Leaf-sheaths keeled; glabrous on surface. Ligule a fringe of hairs; 0.5 mm long. Leaf-blades involute; 15–30 cm long; 1–2.5 mm wide. Leaf-blade surface ribbed; scaberulous; rough abaxially; glabrous; hairless except near base.

INFLORESCENCE Inflorescence a panicle.

Panicle open; pyramidal; 25–45 cm long. Primary panicle branches ascending; 1 -nate; 4–8 cm long. Panicle axis scaberulous. Panicle branches scaberulous.

Spikelets appressed; solitary. Fertile spikelets sessile.

FERTILE SPIKELETS Spikelets comprising 1 fertile florets; without rhachilla extension. Spikelets linear; subterete; 10–12 mm long; breaking up at maturity; disarticulating below each fertile floret. Floret callus evident; 0.5 mm long; pubescent; acute. Floret callus hairs 1–1.5 mm long.

GLUMES Glumes similar; reaching apex of florets; thinner than fertile lemma. Lower glume linear; 9.5–11.5 mm long; 0.9 length of upper glume; membranous. Lower glume surface scabrous. Lower glume apex acute. Upper glume linear; 10–12 mm long; 1 length of adjacent fertile lemma; membranous. Upper glume surface smooth. Upper glume apex acute.

FLORETS Fertile lemma linear; subterete; 10–12 mm long; coriaceous; without keel; 3 -veined. Lemma surface scabrous; rough above. Lemma margins convolute; covering most of palea. Lemma apex awned; 3 -awned. Principal lemma awn 3-branched; spreading; with 24–30 mm long limb; with a straight or slightly twisted column. Column of lemma awn 5–9 mm long. Lateral lemma awns shorter than principal.

FLOWER Anthers 3; 1.6 mm long.

DISTRIBUTION North America: Mexico. South America: Mesoamericana and western South America.

NOTES Aristideae. Fl Costaric 1993.

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