462 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 
First glume usually more than one-third the length of the spikelet, 
if shorter the spikelets not small and blunt. 
Sterile palea enlarged and indurate at maturity, expanding the 
spikelet; blades scarcely wider than their sheaths. 
See Laxa, p. 492. 
Sterile palea if present not enlarged and indurate. 
First glume short, blunt; spikelets pointed; base of culm 
usually decumbent and rooting. 
See DicHoTomiIrLorA, p. 473. 
First glume usually more than one-third the length of the 
spikelet. 
Plants forming conspicuous hard creeping scaly rootstocks. 
See VirGATA, p. 486. 
Plants not forming creeping scaly rootstocks. 
Fruit crested at the apex; spikelets 5.5 to 6 mm. long. 
115. P. zizanioides. 
Fruit not crested. 
Panicles narrow and few-flowered; culms erect and 
wiry; blades drying involute ..See TenERA, p. 490. 
Panicles open or contracted, many-flowered. 
Panicles 40 to 60 cm. long, the numerous elongated 
branches in verticils. .-......- 77. P. megiston. |: 
Panicles mostly much less than 40 cm. long; branches 
not verticillate. 
Spikelets short-pediceled along the nearly simple 
panicle branches.........- 48. P. condensum. 
Spikelets long-pediceled; panicle open at maturity. 
Primary panicles open, the secondary reduced, 
narrow, partly inclosed in the sheaths. 
First glume three-fourths as long as the ellipti- _ 
cal spikelets; fruit apiculate. 
See CoRDOVENSIA, p. 525. 
First glume one-third as long as the pyriform 
spikelets; fruit not apiculate. 
104. P. nodatum. 
Primary and secondary panicles alike, or the 
secondary wanting. 
First glume not pointed, two-thirds the length 
of the spikelet or more; spikelets blunt. 
Panicles not over 6 cm. long; plants some- 
what glaucous, relatively small. 
See ParviIFro.ia, p. 506. 
Panicles 10 to 20 cm. long, very diffuse; 
plants tall, not glaucous. 
Spikelets viscid, 3 min. long. 
75. P. glutinosum. 
Spikelets not viscid, 2 to 2.3 mm. long. 
74. P. millegrana. 
First glume pointed, usually less than two- 
thirds as long as the pointed spikelets. 
Spikelets more or less pubescent. 
Culms slender, straggling; spikelets not 
turgid; glumes and sterile lemma hir- 
sute along the margins. 
72. P. haenkeanum. » 0% 
