324 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM, 
Basal leaves similar to culm leaves, not forming a winter rosette; spikelets 
all fertile. 
Spikelets plano-gibbous, the second glume swollen, bristly and burlike at 
maturity; first glume nearly as long as the minute spikelet; Trinidad. 
75. P. hirtum. 
Spikelets not plano-gibbous nor burlike. 
Fruit transversely rugose. 
Plants perennial. 
Spikelets relatively long-pediceled in a large open panicle. 
20. P. maximum. 
Spikelets subsessile along the racemes or raceme-like branches of 
the panicle. 
Nodes bearded; inflorescence of numerous long subfuasciculate 
ascending racemes ____----------------_---- 5. P. barbinode. 
Nodes glabrous ; inflorescence of several short erect racemes. 
4, P. geminatum., 
Plants annual. (FASCICULATA.) 
Spikelets glabrous. 
Spikelets not over 2 mm. long, not reticulate-veined__6. P. reptans. 
Spikelets 2 to 3 mm. long, strongly reticulate-veined. 
%. P. fasciculatum. 
Spikelets pubescent. 
Plants velvety; rachis pilose ___ ___8. P. molle, 
Plants glabrous as a whole; rachis scabrous only. 
9. P. adspersum. 
Fruit not transversely rugose (minutely papillose-roughened in P. mille- 
grana). 
Plants annual. 
Spikelets pubescent, 1.2 to 1.3 mm. long, long-pediceled in an open 
delicate punicle; blades ovate-lanceolate_____~ 41. P. trichoides, 
Spikelets glabrous, 2 mm. long or more; blades linear or linear- 
lanceolate. 
First glume not over one-fourth the length of the spikelet, truncate 
or triangular-tipped. (DICHOTOMIFLORA in part.) 
Sheaths glabrous _____-_---___________ 10. P. dichotomiflorum. 
Sheaths papillose-hispid______.______________ 11. P. bartowense. 
First glume usually as much as half the length of the spikelet, 
acute or acuminate, (CAPILLARIA.) 
Inflorescence elongate, composed of several approximate implicate 
panicles________-.-.-_--__-----__---___- 16. P. cayennense. 
Inflorescence not composed of approximate nor implicate pan- 
icles. 
Panicles more than half the length of the entire plant; spike- 
lets 2 to 2.2 mm. long__-_-_--------_--__- 14. P. capillare. 
Panicles not more than one-third the length of the entire 
plant; spikelets 3 to 3.8 mm. long______- 15. P. hirticaule, 
Plants perennial. 
Spikelets short-pediceled along one side of the panicle branches, 
forming more or less spikelike racemes. 
Second glume inflated-gibbous, pubescent__-_-___ 45. P. ineptum. 
Second glume not inflated-gibbous. 
Blades lanceolate or ovate-lanceolate, (STOLONIFERA.) 
