I. Panicle somewhat open, the branches elon- 

 gated, ascending - (13) P. auritum 



4. Panicles dense, cylindrical. 



5. Spikelets 4 to 5 nun. long, the outer 



glumes strongly acuminate: aquatic ( 1 2 I P. amplexioaule 

 5, Spikelets 3 mm. long or less ; empty 

 glumes acute or only slightly acu- 

 minate. 

 (I. Panicles dense, cylindrical, 

 about 5 mm thick: spikelets 



3 mm. long... (Mi/', indicvm 



G. Panicles slender, caudiform, 

 about 3 mm. thick ; spikelets 



1.5 mm. long (15) /'. mi/ositniidcs 



3. Spikelets small, in pairs or fascicles on the 



filiform branches of a lax simple panicle, the 



first and second glumes much shorter than the 



third and fourth. ( S B&BVIGLUMK.) 



4. Panicle branches solitary or fascicled, 



elongated, filiform ; spikelets in scattered 



fasciclei (16) P, nodosum 



3. Spikelets solitary, rarely binate, sessiled or pedi- 

 eelled on the slender branches of a decompound 

 open panicle. (SEffusak.) 

 4. First glume equaling the spikelet or nearly 

 so. 

 5. Spikelets obtuse, 1.5 to 2 mm. long. 



(i. Plant 30 to 40 cm. high ; leaves 

 ovate-lanceolate to broadly 

 lanceolate, the base cordate 

 and amplexicaul : spikelets 



1.5 mm. long (17)/'. bnrifoliuiii 



(). Plant 1.5 to 2 m. high, subsean- 

 dent leaves lanceolate ; spike- 

 lets 2 mm. long (25) P. luxurians 



5. Spikelets strongly acuminate, 2 to 

 8.8 mm. long. 

 (J. Spikelets 3 to 3.5 mm. long : 

 leaves about 20 cm. long, 



tuberculate-pilose (27) P. caudiglume 



0. Spikelets 2 to 2 5 mm. long ; 

 leaves 5 cm. long or less, 



glabrous or nearly so (28) /'. mindanaenae 



1. First glume much shorter than the spikelet. 

 5. Annual erect leafy grasses. 



('..Glabrous (20)/'. humile 



(1. More or less pubescent or 

 pilose. 

 7. Spikelets 2 mm. long. 



8. Sheaths strongly 



tuberculate - h i s- 

 pid : leaves and 

 panicles 20 cm. 



long or more (21) P. caesium 



8. Sheaths si i g h t 1 y 

 pilose to subgla- 

 brpus ; leaves and 

 panicles 15 cm. 



long or less (22) /'. Ivsoniense 



7. Spikelets 3 to 4 mm. long. 

 8. Spikelets turgid, 

 o v a t e - o b 1 ong, 

 acute or cuspi- 

 date - acuminate ; 

 panicles thyrsi- 

 forni ; cultivated .... (IS)/', miliaceum 



