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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.

AIRA

EUROPEAN HAIRGRASS

Dieter H. Wilken

Annual
Stems 1–15, generally solitary, sometimes tufted, glabrous to puberulent
Leaves ± basal; collar glabrous to puberulent; ligule < 1 mm, membranous; blade thread-like, flat to rolled
Inflorescence panicle-like
Spikelet bisexual, 3–5 mm; glumes > lower floret, translucent, keel scabrous; callus short-bristly; axis breaking above glumes and between florets; florets 2; lemma faintly 3–5-veined, generally glabrous, tip with 2 slender teeth, slightly scabrous, awned at or below the middle, awn bent once, exserted (sometimes reduced or 0 in lower floret); palea slightly < lemma
Species in genus: ± 10 species: s Eur
Etymology: (Greek: a grass)

Introduced

A. elegantissima Schur

ELEGANT EUROPEAN HAIRGRASS


Stems 1–8, 9–35 cm, generally glabrous
Leaf: sheath and ligule glabrous to slightly scabrous
Inflorescence > 2 cm wide, open
Spikelet 3–4 mm; glumes 2–2.5 mm; lemmas ± 2 mm; awns ± 3 mm
Chromosomes: 2n=14
Ecology: Sandy to clay soils, open sites
Elevation: < 300 m.
Bioregional distribution: c&s Outer North Coast Ranges, Sacramento Valley, San Francisco Bay Area
Distribution outside California: to Washington, eastern&s US; native to s Europe

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