POACEAE. 21 



Fertile stems tall and stout, the sterile 



long and creeping, the nodes densely . 



barbed. 4. P. barbinode. 



Some of the pedicels equaling OP longer 



than the spikelets. 5. P. maximum. 



Panicle branches extending beyond the spikelet 



in a sterile rudiment. 



Spikelets less than 2 mm. long. 6. P. distantiflorum. 



Spikelets 2 mm. long or more. 7. P. Chapmani. 



Fourth scale of the spikelet smooth. 8. P. laxum. 



2. Inflorescence usually a diffuse, rarely narrow panicle, 



its branches not spike-like. 



Fourth scale of the spikelet transversely rugose. 5. P. maximum. 



Fourth scale smooth. 



Annuals, or if perennials, not with tufts of leaves 



at the base of the stem. 



Spikelets lanceolate to ovate, acute to acumi- 

 nate, glabrous ; leaf-blades elongated, 

 linear. 

 Plants tufted, no long creeping rootstocks ; 



spikelets 3 mm. long or less. 

 Panicle narrow, dense, its branches ap- 



pressed. 

 Stems slender, 6 dm. tall or less ; 



basal sheaths round. 9. P. tenerum. 



Stems stout, usually 1 m. tall or 

 more ; basal sheaths compressed, 

 keeled, equitant. 10. P. condensum. 



Panicle broad at maturity, loose and 

 open, its branches spreading or 

 ascending. 



First scale one half as long as the 

 spikelet or more, broadly ovate, 

 acute. 



Sheaths glabrous; stems slender. 11. P. diffusum. 

 Sheaths densely papillose-hispid ; 



stems stout. 12. P. Ghiesbreghtii. 



First scale rarely exceeding one 

 fourth the length of the spikelet, 

 orbicular, truncate or rounded at 



the apex. 13. P. dichotomiflorum. 



Plants with long stout rootstocks ; leaf- 

 blades very thick and firm ; spikelets 4-5 

 mm. long; seacoast grass. 14. P. amarulum. 



Spikelets elliptic, pubescent ; leaf-blades broad, 



ovate-lanceolate. 15. P. trichoides. 



Perennials, with basal tufts of leaves. 



Spikelets 1.5 mm. long, glabrous. 16. P. coerulescens. 



Spikelets 2 mm. long, pubescent. 



Primary leaf-blades 5 mm. wide or less, 

 strongly striate ; spikelets broadly obo- 



yoid. 17. P. neuranthum. 



Primary leaf-blades up to 12 mm. wide ; 



spikelets elliptic. 18. P. nitidum. 



B. Palet much enlarged when mature. 19. P. exiguiflorum. 



1. Panicum geminatum Forsk. Fl. Aegypt.-Arab. 18. 1775. 



Aquatic. Culms 612 dm. long, usually clothed with sheaths below; 

 leaves glabrous, 2.5 dm. long or less, 6-10 mm. wide; racemes 10-20, one-sided, 

 the raehis broadly winged, appressed, 2-4 cm. long; spikelets about 2.5 mm. 

 long, ovate, acute, glabrous, singly disposed in 2 rows, the first scale broader 

 than long and clasping the spikelet at its base, truncate at the apex, the fourth 

 scale transversely wrinkled. 



Wet or moist places, Great Bahama, Abaco, Berry Islands, New Providence, 

 Eleuthera, Cat Island, Great Exuma, Long Island, Fortune Island, Crooked Island, 

 and Inagua : Bermuda ; southern Florida and Texas ; in tropical regions generally. 

 Erroneously referred, by authors, to P. paspaloidcs Pers. WATER-GRASS. 



2. Panicum adspersum Trin. Gram. Pan. 146. 1826. 



Culms ascending or spreading, rooting at the lower nodes, branched, com- 

 pressed, glabrous, 3-10 dm. long. Sheaths ciliate above; leaf -blades 5-20 cm. 



