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POACEAE Barnhart GRAMINEAE Adans., alternate name • Grass Family Lynn G. Clark and Elizabeth A. Kellogg Pl ann or per; usu terrestrial, smt aquatic; tufted, mat-forming, csp, pluricsp, or with solitary culms (flower stems), rhz and stln often well developed. Clm ann or per, herbaceous or woody, usu erect or ascending, smt prostrate or decumbent for much of their length, occ climbing, rarely floating; nd prominent, smt concealed by lf shth; intnd hollow or solid, bases meristematic; brchg from the bas nd only or from bas, mid, and up nd; bas brchg exvag or invag; up brchg invag, exvag, or infvag. Lvs alternate, 2-ranked, each composed of a shth and bld encircling the clm or br; shth usu open, smt closed with mrg fused for all or part of their length; aur (lobes of tissue extending beyond the margins of the sheaths on either side) smt present; lig usu present at the shth-bld jnct, particularly on the adx surface, abx lig common in the Bambusoideae, memb, smt ciliate, adx lig usu present, of memb to hyaline tissue, a line of hairs, or a ciliate membrane; bld usu linear to lanceolate, occ ovate to triangular, bases smt pseudopetiolate (having a petiole-like constriction), venation usu parallel, smt with evident cross veins, occ divergent. Infl (synflorescences) usu compound, composed of simple or complex aggregations of pri infl, aggregations pan, spicate, or rcm or of spikelike br, often with an evident rachis (central axis), pri infl spikelet, pseudospikelet, or spklt equivalents; infl br usu without obvious bracts. Spklt with (0–1)2(3–6) glumes (empty bracts) subtending 1–60 flt, glm and flt distichously attached to the rachilla (central axis); psdspklt with bud-subtending bracts below the glm. Glm usu with an odd number of veins, smt awned. Flt bisex, stmt, or pist, often lat or dorsally compressed, smt round in cross section, usu composed of a lemma (lower bract) and palea (upper bract), lod, and reproductive organs; lm usu with an odd number of veins, often awned, bases frequently thick and hard, forming a cal, backs rounded or keeled over the midvein, awns usu 1(–3), arising bas to tml; pal usu with 2 major veins, with 0 to many additional veins between the major veins, smt also in the mrg, often keeled over the major veins; lod (0)2–3, inconspicuous, usu without veins, bases swelling at anthesis; sta usu 3, smt 1(2) or 6+, filaments capillary, anth versatile, usu all alike within a flt, smt 1 or 2 evidently longer than the others; ov 1-loculed, with (1)2–3(4) sty or sty br, stigmatic region usu plumose. Fruits car, pericarp usu dry and adhering to the seeds, smt fleshy or dry and separating from the seeds at maturity or when moistened; emb 1/5 as long as to almost equaling the car, highly differentiated with a scutellum (absorptive organ), a shoot with lf primordium covered by the coleoptile (shoot sheath), and a root covered by the coleorhiza (root sheath); hila punctate to linear. x = 5, 6, 7, 9, 10, 11, 12. The formulaic name, Poaceae, is based on Poa, the largest grass genus; the alternate name, Gramineae, comes from the Latin, ‘gramen’ grass. The Poaceae or grass family includes approximately 700 genera and 11,000 species. This volume treats 8 subfamilies, 15 tribes, 142 genera, and 483 species. Of these, all the subfamilies and tribes, 88 genera, and 330 species are native to the Intermountain Region. The remaining taxa include introductions, both established and not established, and species cultivated as ornamentals, forage, or food. Grasses constitute the fourth largest plant family in terms of number of species. Nevertheless, the family is clearly more significant than any other plant family in terms of geographic, ecological, and economic importance. Grasses grow in almost all terrestrial environments, including dense forests, open deserts, and freshwater streams and lakes. There are no truly marine grasses, but some species grow within reach of the highest tides. In addition to being widely distributed, grasses are often dominant or co-dominant over large areas. This is reflected in the many words that exist for grasslands, words such as meadow, palouse, pampas, prairie, savanna(h), steppe, and veldt. Not surprisingly, grasses are of great ecological importance as soil stabilizers and as providers of shelter and food for many different animals. The economic importance of grasses to humans is almost impossible to overestimate. The wealth of individuals and countries is dependent on the availability...

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