Aristida

Aristida is a genus of herbaceous plants belonging to the Poaceae family.

It comprises 747 described species and of these, only 298 accepted.

Description

They are annual or generally perennial plants, cespitose, rarely rhizomatous; stems cylindrical or compressed, usually solid; hermaphrodite plants. Ligule a minute, ciliolate membrane; sheets linear, flattened to folded or convoluted. Inflorescence a panicle, solitary, terminal, open to spiciform; spikelets solitary, more or less terete, pedicelate, with 1 bisexual floret; disarticulation above glumes; glumes frequently almost as long as the lemma, equal or unequal, membranaceous, narrow, acuminate, keeled, 1–3 (–5)-veined, entire or emarginate, muticous or briefly awned, the lower generally disarticulating much earlier than the upper; lemma terete, convoluted or involute, 3-veined, rigid, sometimes ending in a narrow column, straight or twisted, articulated or not, margins overlapping palea; awns generally 3, terminal, usually glabrous, the central one as long as a longer than the laterals, rarely the 2 laterals rudimentary or absent; palea small, much shorter than lemma, hyaline or membranaceous; callus usually hairy, obtuse or pointed, rarely 2-fidus; lodicules 2; stamens 1 or 3; styles 2. Fruit a caryopsis, sulcate or non-sulcate; linear thread; embryo 1/3–1/2 the length of the caryopsis.

Taxonomy

The genus was described by Carlos Linnaeus and published in Species Plantarum 1: 82. 1753. The type species is: Aristida adscensionis L.

Etymology

The name of the genus comes from the Latin Arista or from the Greek Aristos (bristles, or corn awns).

Cytology

The basic chromosome number of the genus is x = 11 and 12, with somatic chromosome numbers of 2n = 22, 24, 36, 44, 48 and 66, since there are diploid species and a polyploid series. Relatively "small" chromosomes. Persistent nucleoli.

Selected species