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POACEAE

GRASS FAMILY

James P. Smith, Jr., except as specified

Annual to bamboo-like; roots generally fibrous
Stem generally round, hollow; nodes swollen, solid
Leaves alternate, 2-ranked, generally linear; sheath generally open; ligule membranous or hairy, at blade base
Inflorescence various (of generally many spikelets)
Spikelet: glumes generally 2; florets (lemma, palea, flower) 1–many; lemma generally membranous, sometimes glume-like; palea generally ± transparent, ± enclosed by lemma
Flower generally bisexual, minute; stamens generally 3; stigmas generally 2, generally plumose
Fruit: achene-like grain
Genera in family: 650–900 genera; ± 10,000 species: worldwide; greatest economic importance of any family (wheat, rice, maize, millet, sorghum, sugar cane, forage crops, ornamental, weeds; thatching, weaving, building materials)
Reference: [Hitchcock 1951 Manual grasses US, USDA Misc Publ 200; Clayton & Renvoise 1986 Kew Bull Add Series 13]
See Glossary p. 26 for illustrations of general family characteristics. Generally wind-pollinated.

ARISTIDA

THREE-AWN

Kelly W. Allred

Annual, perennial herb, cespitose
Stem ascending to erect
Leaves basal and cauline; basal often tufted; ligule hairy; blades flat or inrolled
Inflorescence raceme-like or panicle-like; branches spike-like
Spikelet: glumes narrowly lanceolate, thin, 1-veined, awn generally 0; floret 1, breaking above glumes; lemma ± fusiform, hard when mature, 3-veined, tip beak-like or not, awned at tip, awns 3, equal or unequal; palea < lemma, enclosed by lemma, transparent
Fruit narrowly fusiform
Species in genus: ± 300 species: worldwide, arid warm temp. Some species noxious
Etymology: (Latin: awn)
Reference: [Allred 1992 Great Basin Nat 52:41–52]

Native

A. divaricata Willd.

POVERTY THREE-AWN

Perennial
Stem erect, 2.5–7 dm
Leaf: blade 5–20 cm, loosely inrolled, glabrous
Inflorescence 10–30 cm, 6–25 cm wide, open; stalk flattened, easily broken; primary branches stiffly spreading
Spikelet: glumes ± equal, 8–12 mm; lemma 8–13 mm, twisted 4 or more times at tip, awns generally 10–22 mm, lateral < or = central; anthers 0.8–1 mm
Chromosomes: 2n=22
Ecology: Uncommon. Dry slopes, scrub, grassland
Elevation: < 1000 m.
Bioregional distribution: s San Joaquin Valley, South Coast, s Peninsular Ranges
Distribution outside California: to Great Plains, C.America
Plants with lateral awns much < central or absent are A. orcuttiana Vasey, once collected near San Diego.

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