352 
4. Panicle somewhat open, the branches elon- 
gated, ascending 
4. Panicles dense, cylindrical. 
5. Spikelets 4 to 5 mm. long, the outer 
glumes strongly acuminate ; aquatic 
5. Spikelets 3 mm. long or less ; empty 
glumes acute or only slightly acu- 
minate. 
6. Panicles dense, cylindrical, 
about 5 mm. thick ; spikelets 
3 mm. long 
- 6. Panicles slender, caudiform, 
about 3 mm. thick ; spikelets 
1.5 mm. long , 
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. (§ Breviglume.) 
4. Panicle branches solitary or fascicled, 
elongated, filiform ; spikelets in scattered 
fascicles 
3. Spikelets solitary, rarely binate, sessiled or pedl- 
celled on the slender branches of a decompound- 
open panicle. (§Effusab.) 
4. First glume equaling the spikelet or nearly 
(13) P. auritum 
(12) P. amplexicaule 
(14) P. mdiCAmi 
(15) P. myosuroides 
(16) P. nodosum 
5. Spikelets obtuse, 1.5 to 2 mm. long. 
6. Plant 30 to 40 cm. high ; leaves 
ovate-lanceolate to broadly 
lanceolate, the base cordate 
and amplexicaul ; spikelets 
1.5 mm. long 
6. Plant 1.5 to 2 m. high, subscan- 
dent leaves lanceolate ; spike- 
lets 2 mm. long 
5. Spikelets strongly acuminate, 2 to 
3.5 mm. long. 
6. Spikelets 3 to 3.5 mm. long; 
leaves about 20 cm. long, 
tuberculate-pilose 
6. Spikelets 2 to 2.5 mm. long ; 
leaves 5 cm. long or less, 
glabrous or nearly so 
4. First glume much shorter than the spikelet. 
5. Annual erect leafy grasses. 
6. Glabrous 
6. 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 
8. Sheaths si i g h t 1 y 
pilose to subgla- 
brous ; leaves and 
panicles 15 cm. 
long or less 
7. Spikelets 3 to 4 mm. long. 
8. Spikelets turgid, 
ovate-obl ong, 
acute or cuspi- 
date - acuminate ; 
panicles thyrsi- 
form ; cultivated ... 
(17) P. hrevifolium 
(25) P. luxiirians 
(27) P. caudiglume 
(28) P. mindanaense 
(20) P. humilc 
(21) P. caesium 
(22) P. luzoniense 
(18) P. miliaceum 
