Aristida adscensionis L.

Global description

Aristida adescensionis is a small plant with long alternating linear leaves. The sheath is ciliated on the margin. The ligule is ciliated. The limb is scabrid on the upper side and often convoluted. The inflorescence is a narrow panicle with uniflorous spikelets 7 to 10 mm long. They have scabrous linear glumes and a lemma, longer than the glumes, with scabrid margin and at the summit surmounted by 3 scabrous awns.

First leaves

The first leaves have a rolled prefoliation. They are carried by short sheaths of 1 to 2 cm. The blade is very narrow, often convoluted and 5 to 10 cm long. The ligule is short and ciliate. The apex of the limb is long tapered.

General habit

Aristida adscensionis is sparsely tufted and usually erected. This species has low tillering. The individuals are most often solitary and slender or in small tufts. The plant is 10 cm to 1 m tall.

Underground system

The roots are fasciculate.

Culm

The culm is cylindrical or slightly compressed, glabrous and smooth. It is most often knotted and the nodes are tinged with purple. The culm is ramified in its upper part.

Leaf

The leaves are alternate, light green in color and sometimes tinged with purple at the base of the sheaths. The sheath is glabrous with margin finely ciliate. It presents a round hull little marked. The ligule is ciliated and 0.6-0.8 mm high. The blade is narrow, 2 to 3 mm wide and often convoluted. It is linear and 5 to 20 cm long and ends with a long tapered peak. The margin is scabrous. The lower surface is glabrous while the upper surface is scabrous more particularly along two more prominent lateral veins. The central vein is slightly thickened.

Inflorescence

The inflorescence is a slightly spreading panicle 4 to 6 cm wide and 10 to 30 cm long, with some short branches at the base. It is light green to purple in color. The branches and spikelets generally hang on the same side of the axis because of the inclination and the curvature of the top of the inflorescence.

Spikelet

Spikelets are all alike. They have a single, bisexual flower. They are flattened and measure 7 to 10 mm long and 0.5 mm wide. The glumes are linear with emarginated or cunate apex. The dorsal rib is scabrous. The lower glume is 4 to 7 mm long, while the upper glume is 5 to 10 mm long. The lemma is 8 to 12 mm long and protrudes above the glumes. The margin is scabrid in its upper half. The top of the lemma is surmounted by three awns 7 to 25 mm long and scabrous. Palea is shorter than lemma and membranous. The flower has 2 stigmas and 3 stamens.
At maturity, the spikelet disarticulates above the glumes revealing, at the base of the lemma, a short racheole of 0.5 mm, pubescent.

Grain

The grain is linear, 4 mm long. During the spread, it remains locked in the palea and the lemma that become hard at maturity.

https://www.gbif.org/species/2706277