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(Last Modified On 10/16/2012)
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(Last Modified On 10/16/2012)
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Family
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POACEAE
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Description
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Flowers perfect (rarely unisexual), arranged in spikelets consisting of a short- ened axis (rachilla) and 2 to many 2-ranked bracts, the lowest two (glumes, rarely one or both obsolete) empty, each succeeding one or more (lemmas) bearing in their axils a single flower (one to few of the lower lemmas sometimes barren, and the upper one or more often reduced and sterile), and between the flower and rachilla a 2-nerved bract (palea), the lemma, palea, and included flower consti- tuting the floret; stamens 1 to many, usually 3, with delicate filaments and 2- celled anthers; pistil 1, with a 1-celled 1-ovuled ovary, 2 (rarely 1 or 3) styles, and usually plumose stigmas; fruit a caryopsis, the grain rarely free from the peri- carp. Herbaceous or sometimes woody plants with round or somewhat flattened, hollow or solid stems (culms), and 2-ranked, usually parallel-veined leaves con- sisting of a sheath which envelops the culm, a blade, usually flat, and between the two on the inside a membranaceous or hairy appendage (ligule), this rarely obsolete.
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Key
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a. Plants with woody culms, erect or often clambering. Blades petioled. (BAMBUSEAE.) (See also Lasiacis.) b. Culms in large erect clumps, usually 10 m. or more high; stamens 6; spikelets several-flowered. c. Culms thornless; keels of palea wingless I. BAMBUSA cc. Culms thorny; keels of palea winged 2. GUADUA bb. Culms clambering, or if erect, much less than 10 m. high. Sterile lemmas 1 or 2 below the fertile florets. c. Spikelets with 2 or more perfect florets - ---3. ARTHROSTYLIDIUM cc. Spikelets with 1 perfect floret 4. CHUSQUEA aa. Plants herbaceous (woody in Lasiacis with subglobose spikelets). b. Spikelets 1- to many-flowered, the reduced florets, if any, above the fertile florets (lower florets empty in Uniola and Ctenium); articu- lation usually above the glumes (below the glumes in Zeugites, Cinna, Polypogon, Oryza, and Leersia). c. Spikelets in groups of 2-5, the groups racemose along a common axis, falling entire. d. Groups of spikelets nodding; first glumes relatively thin, not forming an involucre - 36. AEGOPOGON dd. Groups of spikelets erect, the first glumes broad, indurate, forming a pitcher-shaped involucre around the spikelets - 27. ANTHEPHORA cc. Spikelets solitary or paired, not arranged in groups along a com- mon axis. d. Lemma with a long much-contorted awn, the awns becoming tangled and remaining attached at the apex of the axis. Broad- leaved perennials - --5. STREPTOCHAETA dd. Lemma awnless, or, if awned, the awn straight or geniculate, never contorted or becoming tangled. e. Spikelets unisexual. Plants monoecious. f. Spikelets arranged in whorls in a dense spike, each whorl consisting of a sessile pistillate spikelet surrounded by 4 or 5 staminate pedicellate spikelets; stamens numerous - 69. PARIANA ff. Spikelets paniculate. g. Spikelets in somewhat distant pairs along the main branches, one of each pair sessile, pistillate, the other long-pedicellate, staminate, much smaller than the pistil- late spikelet; stamens 6 - 39. PHARUS gg. Spikelets not in pairs as above; stamens 2 or 3. h. Glumes wanting, only the lemma and palea present; aquatic grasses with the staminate and pistillate spike- lets in separate inflorescences-- 40. LUZIOLA hh. Glumes present; terrestrial, usually forest grasses. (OLYREAE). i. Panicles large, terminal, the pistillate spikelets on the upper branches and toward the ends of the lower (9) [VOL. 30 106 ANNALS OF THE MISSOURI BOTANICAL GARDEN ones, the staminate on the lower part of the lower branches _ _--- 58. CLYRA ii. Panicles small, axillary, or terminal and axillary, the terminal when present usually wholly staminate. j. Fruit roughly triangular, inflated, gibbous; pani- cles axillary, composed of 1 terminal pistillate spikelet, and a few staminate spikelets below it--- 65. LITHACHNE jj. Fruit subcylindric; panicles terminal and axillary. k. Fruit sessile; terminal panicle, if present, wholly staminate, the axillary usually pistillate, or rarely with a few staminate or sterile spikelets on the lower branches - --66. RADDIA kk. Fruit raised on the enlarged and thickened segment of the rachilla -- - 67. CRYPTOCHLOA ee. Spikelets perfect, or if unisexual, the plants dioecious. f. Spikelets sessile or short-pedicellate on one side of a con- tinuous rachis. (CHLORIDEAE). g. Spikelets 1-flowered with no rudimentary florets above the fertile one. Rachilla prolonged beyond the floret as a naked stipe __31. CYNODON gg. Spikelets 2- to several-flowered, or, if only 1-flowered, with one or more rudimentary florets above the perfect one. h. Spikes digitate. i. Lemma awnless or awn-pointed. j. Rachis prolonged beyond the spikelets in a naked point ... 3O. DACTYLOCTENIUM ji. Rachis not prolonged _ - - _ - _ 9. ELEUSINE ii. Lemma awned. Rudiment narrow or club-shaped, composed of one or more reduced sterile lemmas. 34. CHLORIS hh. Spikes solitary or racemose. i. Spikes solitary, rarely two or three. Spikelets with two sterile florets below the fertile one. Second glume with a stout divergent awn at the middle 32. CTENIUM ii. Spikes several to many, racemose. j. Lemma entire or minutely bifid, awnless or 1- awned. k. Rudimentary floret 1-awned, sometimes re- duced to one or two bristles, rarely wanting. 33. GYMNOPOGON kk. Rudimentary floret awnless-- _28. LEPTOCHLOA jj. Lemma variously lobed or dentate, usually 3- awned _ ______3 5. BOUTELOUA ff. Spikelets pedicellate in open or contracted panicles (sessile in loose spikes in Jouvea). g. Spikelets 2- to several-flowered. h. Lemmas awnless or awned from the tip, sometimes from between the teeth of a minutely bifid apex. (FESTUCEAE). i. Lemma or rachilla villous with long silky hairs (staminate spikelets glabrous in Gynerium). Tall stout reeds. j. Plants dioecious. Culms very high with short internodes _ ---- I4. GYNERIUM jj. Plants with perfect flowers. k. Lemma and rachilla hairy; blades crowded at the base of the culms -- ---- 3 CORTADERIA kk. Lemma naked, rachilla hairy; blades distrib- uted along the culms _- _ _ _ _ _ I2. PHRAGMITES ii. Lemma and rachilla glabrous or pubescent but not with long silky hairs. j. Plants dioecious. Staminate spikelets many-flow- ered, rather distant in a loose spike, the pistillate solitary or clustered, nearly hidden in the leaves- I8. JOUVEA jj. Plants with perfect flowers. (1 0) 1 943] FLORA OF PANAMA (Gramineae) 107 k. Blades ovate to lanceolate with conspicuous transverse veins, most of them distinctly pedi- cellate. 1. Glumes narrow, acute, without transverse veins. Panicles usually large, the spikelets borne only at the ends of the fragile filiform branchlets _-- _ _ i6. ORTHOCLADA 11. Glumes broad with prominent transverse veins, the summit irregularly toothed- I7. ZEUGITES kk. Blades linear with no transverse veins. 1. Stigmas elongate, tendril-like. Spikelets distant in a long narrow 1-sided raceme I 15. STREPTOGYNE 11. Stigmas not elongate. m. Lemma 3-nerved, the palea usually per- sistent 10. ERAGROSTIS mm. Lemma 5- to several-nerved, the nerves sometimes obscure. n. Spikelets with 1-4 empty lemmas be- low the fertile florets, large and very flat_ ___ _ _ 1. UNIOLA nn. Spikelets with no empty lemmas below the fertile florets. o. Lemmas densely pubescent on the nerves, awnless, keeled _ __ 9. POA oo. Lemmas glabrous, or pubescent all over. p. Spikelets short-pedicellate, rather distant in a simple raceme - 7. BRACHYPODIUM pp. Spikelets in open or contracted panicles. q. Lemma awned from between the teeth of the minutely bifid apex, conspicuously compressed - 6. BROMUS qq. Lemma awnless or awned from the tip, rounded or obscurely keeled - - _ - 8. FESTUCA hh. Lemma awned from the back. Glumes as long as the lowest floret, usually about as long as the spikelet. (AvENEAE.) I9. TRISETUM gg. Spikelets 1-flowered. h. Spikelets strongly laterally compressed; glumes minute or wanting; articulation below the spikelet. (ORYZEAE). i. Glumes minute; lemmas often awned _ _ 37. ORYZA ii. Glumes wanting; lemmas awnless _ - _ 3 8. LEERSIA hh. Spikelets terete, or at least not strongly compressed; glumes usually well developed; articulation above the glumes (below the glumes in Cinna and Polypogon). (AGROSTIDEAE). i. Glumes awned 22. POLYPOGON ii. Glumes awnless, or, if awned, much shorter than the floret. j. Lemma with a very short awn from just below the apex CINNA jj. Lemma awnless or with a well-developed awn. k. Fertile spikelets surrounded by numerous sterile spikelets in the form of bristles or delicate bracts 23. PEREILEMA kk. Spikelets all perfect, not surrounded by bristles. 1. Palea wanting; lemma awnless or awned from the back- _ - _ _ - 20. AGROSTIS 11. Palea well developed; lemma awnless or awn- ed from the tip. (11) [VOL. 30 108 ANNALS OF THE MISSOURI BOTANICAL GARDEN m. Awn simple; lemma firm but not in- durate; callus blunt, glabrous (sometimes pubescent or villous in Muhlenbergia). n. Lemma 3-5-nerved, mucronate or awned 24. MUHLENBERGIA nn. Lemma 1-nerved, obtuse or subacute 25. SPOROBOLUS mm. Awn trifid, the lateral ones sometimes reduced or wanting; lemma indurate; callus sharp, bearded _ - z6. ARISTIDA bb. Spikelets with 1 perfect terminal floret and a sterile or staminate floret below it (both florets usually fertile in Isachne); articulation below the glumes (except in Arundinella), either in the pedicel, the rachis, or at the base of a cluster of spikelets. c. Glumes membranaceous; fertile lemma indurate or at least as firm as the glumes; sterile lemma like the glumes in texture. d. Fertile lemma scarcely firmer than the glumes, awned, the awns relatively long, geniculate 41. ARUNDINELLA dd. Fertile lemma usually much firmer than the glumes, awnless or awn-tipped. (PANICEAE). e. Spikelets subtended by bristles or enclosed in spiny burs. f. Spikelets subtended by bristles. g. Bristles persistent _ - -_ - _ 6z. SETARIA gg. Bristles deciduous, falling with the spikelet -63. PENNISETUM ff. Spikelets enclosed in spiny burs - 64. CENCHRUS ee. Spikelets neither subtended by bristles nor enclosed in spiny burs. f. Spikelets arranged on one side of spike-like racemes. g. Margins of fertile lemma thin, not inrolled. h. Spikelets densely covered with long tawny silky hairs 43. TRICHACHNE hh. Spikelets glabrous or pubescent but not long-silky - 44. DIGITARIA gg. Margins of fertile lemma inrolled, indurate. h. Rachilla joint and first glume adnate, forming a swollen ring-like callus - -- -- 49. ERIOCHLOA hh. Rachilla joint and first glume neither adnate nor swollen. i. Racemes solitary (see also Paspalum). j. Spikelets sunken in a thick corky rachis; rachis disarticulating at maturity -45. STENOTAPHRUM ji. Spikelets not sunken in a thick corky rachis; rachis not disarticulating at maturity. k. Rachis rather broadly winged, partially en- folding the spikelets; spikelets paired but rath- er distant, appearing as if solitary in a single row, the spikelets of each pair placed back to back _ - -------- - _ 46. THRASYA kk. Rachis wingless; spikelets solitary, the backof the fertile lemma turned from the rachis - 48. MESOSETUM ii. Racemes 2 to many (sometimes solitary in Paspalum)n. j. Spikelets awned or awn-pointed. k. First glume long-awned, the body nearly as long as the spikelet; spikelets glabrous or pubescent but not hispid - - _ __ 6o. OPLISMENUS kk. First glume awnless, less than half as long as the spikelet; spikelets hispid _ - _- __ 6i. ECHINOCHLOA ij. Spikelets awnless. k. Fertile lemma with small wings at the base, these sometimes reduced to scars -- 54. ICHNANTHUS kk. Fertile lemma wingless. 1. First and second glume equal, nearly as long as the spikelet, the second becoming spiny at maturity. Racemes loosely flowered- - 47. PSEUDECHINOLAENA 11. First glume not more than half as long as the spikelet, or wanting, the second as long as the spikelet, glabrous or pubescent but not spiny. m. Back of the fruit turned away from the rachis. (12) 1943] FLORA OF PANAMA (Gramineae) 109 n. First glume well developed - 50. BRACHIARIA nn. First glume wanting_- _S I . AXONOPUS mm. Back of the fruit turned toward the rachis. n. First glume always present --_ 53. PANICUM nn. First glume usually wanting (often present in P. langei and occasionally in other species) _ - ___ 52. PASPALUM ff. Spikelets paniculate (panicles dense and spike-like in Sac- ciolepis and Hymenachne amplexicaulis). g. Spikelets villous with appressed or spreading hairs; first glume wanting -_- - 42. LEPTOCORYPHIUM gg. Spikelets glabrous or pubescent; first glume always present. h. Fertile lemma with small wings at the base, these sometimes reduced to scars 54. ICHNANTHUS hh. Fertile lemma wingless. i. Spikelets with 2 fertile florets 59. ISACHNE ii. Spikelets with only I fertile floret. j. Second glume inflated, saccate at the base; spike- lets unsymmetrical 56. SACCIOLEPIS jj. Second glume not inflated; spikelets symmetrical. k. First and second glume equal, similar, as long as the spikelet. Plants widely decumbent- spreading - 58. HOMOLEPIS kk. First glume rarely more than half as long as the second, dissimilar. 1. Panicles dense, spike-like or with narrowly ascending branches; fruit scarcely indurate, open at summit - -- - 57. HYmENACHNE 11. Panicles mostly open, loosely flowered, fruit indurate, closed at summit, the lemma tight- ly enclosing the palea. m. Spikelets with a tuft of woolly hairs at the tip of the second glume and sterile lemma; plants woody, clambering- - 55. LASIACIS mm. Spikelets without woolly hairs; plants herbaceous - - - - 53. PANICUM cc. Glumes indurate; fertile lemma hyaline or membranaceous, the sterile lemma like the fertile one in texture; spikelets arranged in pairs in narrow spikes or racemes. d. Spikelets with perfect flowers, each perfect spikelet usually paired with a staminate or reduced sterile spikelet, or sometimes all the spikelets perfect and alike. (ANDROPOGONEAE). e. Racemes paniculate. (See also Andropogon saccharoides). f. Panicles conspicuously silky; spikelets awnless. g. Panicles white or pinkish, loose but rather dense. h. Rachis continuous; spikelets unequally pedicellate - 70. IMPERATA hh. Rachis breaking up at maturity; lower spikelet sessile, the upper pedicellate- 7 1. SACCHARUM gg. Panicles golden brown, very dense and compact - 72. ERIOCHRYSIS ff. Panicles not silky; spikelets awned. Racemes reduced to one or few joints. g. Pedicellate spikelet staminate- 78. SORGHUM gg. Pedicellate spikelet wanting, the pedicel only present 79. SORGHASTRUM ee. Racemes solitary, paired, or digitate, sometimes aggregate in a large compound inflorescence, if paniculate, the racemes crowded in a dense, silky, terminal panicle. f. Spikelets all perfect, alike. g. Racemes solitary at the ends of the branches; spikelets awned ---73. POLYTRIAS gg. Racemes digitate; spikelets awnless-- 82. ISCHAEMUM ff. Spikelets of each pair unlike, the lower sessile, perfect, the upper pedicellate, usually reduced (conspicuous in Hackel- ochloa and Diectomis). g. Spikelets awnless. (13) [VOL. 30 110 ANNALS OF THE MISSOURI BOTANICAL GARDEN h. Plants annual; rachis joint and the pedicel of the upper spikelet grown together. First glume of sessile spikelet globose, alveolate 83. HACKELOCHLOA hh. Plants perennial; rachis joint and pedicel distinct. i. Rachis joints and pedicels much thickened at the summit, glabrous; pedicellate spikelet rudimentary. 84. MANISURIS ii. Rachis joints and pedicels not much thickened at the summit; pedicellate spikelet staminate or neuter- 81. ELYONURUS gg. Spikelets, at least the fertile ones, awned. h. Culms simple, usually with a single terminal erect raceme; awns plumose, 3-5 cm. long - ---- 80. TRACHYPOGON hh. Culms branching, at least toward the summit; awns glabrous or scabrous. i. Pedicellate spikelet conspicuous, the first glume broad, awned, obscuring the spikelets; awn of fertile lemma 4-5 cm. long, geniculate; plants annual-- 75. DIECTOMIS ii. Pedicellate spikelet inconspicuous; awn of fertile lemma usually less than 15 mm. long; plants per- ennial. j. First glume sharply 2-keeled, at least toward the summit. k. Spikelets of all pairs unlike, the sessile fertile, the pedicellate sterile - 74. ANDROPOGON kk. Spikelets of the lower pairs alike, staminate or neuter - _ - _ 776 . CYMBOPOGON jj. First glume of sessile spikelet rounded on the back, the margins involute - _---___-_ _-77. HYPARRHENIA dd. Spikelets unisexual, the staminate and pistillate spikelets in separate inflorescences or the staminate above and the pistillate below in the same spike. e. Staminate spikelets in a terminal tassel, the pistillate in the axils of the leaves ---- - _- _-- __87. ZEA ee. Staminate spikelets above, the pistillate below in the same spike. f. Spikes short, the 1- or 2-flowered pistillate portion enclosed in a bead-like sheathing bract -- - -86. Coix ff. Spikes elongate, many-flowered, the pistillate portion break- ing up into joints, not enclosed in a sheathing bract--- 85. TRIPSACUM
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