24 POACEAE 



Glumes broad, several-toothed or several-awned. 73. Triticum. 

 Glumes not toothed, 1-awned or awnless. 



Peremiials; spikelets several-flowered. 72. Agroptron. 



Annuals or biennials; spikelets 2-flowered. 74. Secale. 



Empty glumes with their back turned to the rachis. 71. Loltom. 

 Spikelets 2-6 at each node of the rachis, or if solitary the empty glumes arranged obliquely 

 to the racliis. 



Spikelets 1-flowered or with a rudimentary second flower. 75. Hordedm. 

 Spikelets 2-many-flowered. 



Racliis of spikes articulated, readily breaking up into joints. 76. Sitanion. 

 Racliis of spikes continuous, not breaking up into joints. 



Empty glumes well developed. 77. Elymus. 



Empty glumes wanting or reduced to short bristles. 78. Hystrix. 



1. SCHIZACHYRIUM Nees. Beard-grass, Bunch-grass, i. S. scoparium. 



2. AMPHILOPHIS Nash. Beard-grass. l. A. saccharoidcs. 



3. ANDROPOGON (Royen) L. Bluestem, Beard-grass. 



Lemma of the sessile spikelets with a long geniculate awn, more or less spiral at the base. 

 Outer two glumes of the sessile spikelets more or less hispidulous all over; hairs of the 

 racliis-internodes usually 2 mm. long or less, mostly wliite. 1. A. provincialis. 



Outer two glumes of the sessile spikelets smooth or nearly so, except on the nerves; 

 hairs of the raclii.s-tnternodes 3-4 mm. long, usually yellow. 2. A. chrysocomus. 

 Lemma of the sessile spikelets awnless or with a short straight untwisted awn. 

 Marginal hairs of the pedicels and rachis-internodes copious, stiff. 3. A. Hallii. 

 Marginal hairs of the pedicels and rachis-internodes scant, lax, crisp, or almos't 

 wanting. 4. A. paucipilus. 



4. SORGHASTRUM Nash. Indian Grass. i. S. nutans. 



5. HOLCUS L Johnson Grass, Broom Corn, Sugar Corn. i. H. halapensc. 



6. PLEURAPHIS Torr. Black Bunch-grass, Galleta Grass, 



Tobosa Grass. 



Stem and leaf-sheath, at least the lower ones, densely woolly. 1. P. rigida. 



Stem and leaf-sheath not woolly. 



Outer glumes of the spikelets cuneate, awnless ; nerves strongly divergent. 



2. P. mulica. 



Outer glumes linear or oblong, awned; nerves parallel. 3. P. Jamesii. 



7. PASPALUM Jj. Paspalum. l. P. stramineutr . 



8. SYNTHERISMA Walt. Crab-grass. 



Pedicels terete or nearly so, sparingly if at all hispidulous; lower sheaths glabrous; lerani 

 brown in fruit. 

 Spikelets more than 2 mm. long. 1. S. Ischaemum 



Spikelets 1.2.5-1.5 mm. long. 2. S. paniceum. 



Pedicels sharply 3-angled, the angles strongly hispidulous, as also the sheath; lemma 

 wliite in fruit. 

 Spikelets about 2.5 mm. long; third glume with the nerves strongly hispid above the 



middle. 3. S. sanguinale. 



Spikelets 3 mm. long or more; third glume with the nerves smooth or nearly so. 



4. S. marginatum. 



9. VALLOTA Chase. l. v. sacchamtn. 



10. PANICUM L. Panic-grass, Witch-grass. 



Inflorescence truly paniculate. 



Basal leaf-blades long and narrow; spikelets lanceolate or ovate, acute or acuminate. 

 Annuals. 



Branches of the panicle widely spreading, the well developed pulvinus in their 

 a.xils long-hairy; spikelets lanceolate, acuminate. 1. P. barbipuhinatum. 

 Branches of the panicle ascending, rarely spreading, the pulvinus glabrous or 

 sparingly hairy; spikelets ovate to ellipsoid, acute. 2. P. capillare. 

 Perennials, with long scaly rootstocks and stolons. 3. P. tirgatum. 



Basal leaf-blades ovate to lanceolate, obtuse. 

 Spikelets less than 2 mm. long. 



Stem and sheaths sparingly pubescent, with spreading papillate hairs. 

 Vernal leaves glabrous or nearly so on the upper side. 



Autumnal stems brandling from the lower nodes, forming a spreading 



bunch, 1-1.5 dm. liigh. 4. P. occidentale. 



Autumnal stems branching from the middle nodes, forming widely 

 spreading mats. 5. P. tennesseense. 



Vernal leaves pubescent on the upper side, especially towards the base. 

 Spikelets 1.8-2 mm. long; autumnal form decumbent- spreading. 



6. P. pacificum. 

 Spikelets 1.6-1.8 mm. long; autumnal form not decumbent-spreading. 



7. P. Huachucae. 



