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.

TRISETUM

Dieter H. Wilken

Annual, perennial herb
Stems ascending to erect
Leaves basal and cauline; ligule membranous, obtuse to truncate, toothed, tip ciliate or not; blade flat to inrolled
Inflorescence panicle- to spike-like, open to compact, cylindric to narrowly conic
Spikelet: glumes ± unequal, generally = or < lower floret, keeled, acute, lower 1-veined, upper 3-veined; axis stiff- to soft-hairy, generally prolonged behind upper floret, bristly or with vestigial floret; florets 2–3, bisexual, breaking above glumes and between florets (sometimes below glumes); callus short-hairy; lemmas ± keeled, tip 2-bristled or not, awned on back near tip or not, awn straight to bent; palea = or < lemma
Species in genus: 50–70 species: temp, tropical mtns
Etymology: (Latin: three bristle)
Some species intergrade; needs critical study in w North America.