90 POACEAE 
Plant green: stems slender: leaf-blades 
rather sparingly pubescent. 102. P. pedicellatum. 
Plant purplish: stems stout: leaf-blades 
densely pubescent. 108. P. malacon. 
Pubescence of widely spreading hairs. 
Stems, as well as the leat-sheaths, densely 
velvety pubescent, usually 6-8 dm. ` 
tall. 106. P. scoparium. 
Stems, as well as the leaf-sheaths, papil- 
lose.pubeseent with rather stiff long 
hairs, usually less than 4 dm. tall. i5: 
** Middle leaf-blades of the main stem more than 1.5 em. wide, some- 
times 3-4 cm. in width, the base cordate and clasping. 
Spikelets 3 mm. long or less. 
Leaf-blades glabrous, or sometimes ciliate on the margins. 
Spikelets 1.5 mm. long. 92. P. polyanthes. 
Spikelets 2-3 mm, long. 
Leaf-sheaths glabrous, or sometimes ciliate on the margin. 
Basal leaf-blades smaller than those of the stem. 
Stems erect, even in the late state, sparingly branched: 
x 
malocophyllum, 
spikelets obtuse or acutish. 111. P. commutatum. 
Stems finally much-branched and prostrate, forming 
large mats: spikelets very acute. 110. P. Manatense. 
Basal leaf-blades usually very long, larger than those of 
the stem : 
Their margin naked. 113. P. Joorii. 
Their margin ciliate with long hairs. 112. P. mutabile. 
Leaf-sheaths, at least the lower ones and those of the 
branches, densely papillose-hispid. 114. P. clandestinum. 
Leaf-blades pubescent : : 
Ovate-lanceolate: stems pubescent with short ascending 
. hairs. 109. P. ovale. 
Linear: stems densely velvety pubescent with spreading 
hairs. 106. P. scoparium. 
Spikelets exceeding 3 mm. long. 
gni enna on the stem and leaf-sheaths, if any, of soft weak 
airs. 
Nodes naked: leaf-blades usually ciliate on the margin. 120. P. macrocarpon. 
Nodes densely barbed with spreading hairs: leaf-blades usu- 
ally naked on the margins. 
Lower surface of the leaf-blades paler, glabrous. 121. P. Porterianum. 
Lower surface of the leaf-blades pubescent, as are also the gee! 
sheaths and stems. . 122. P. pubifolium. 
Pubescence on the stem and leaf-sheaths of coarse rigid hairs is 
arising from manifest papillae. 119. P. Ravenelii. 
IX. LATIFOLIA. 
Tropical plants represented in our range by a single species. 123. P. latifolium. 
1. Panicum prostratum Lam. Stems prostrate and creeping, leafy, branching, the 
summit ascending : leaf-blades ovate, glabrous or pubescent, ciliate on the margin near the 
cordate-clasping base, usually 1-3 cm. long, sometimes larger: racemes 4-6, ascending, 
one-sided, 1.5-2.5 cm. long : spikelets about 2 mm. long, elliptic, glabrous, acute, the first 
scale broader than long, truncate at the apex, the fourth scale transversely rugose. 
Along roadsides, Louisiana. Introduced from tropical countries. Summer and fall. 
2. Panicum obtisum H.B.K. Glabrous. Stems erect, simple, or branching at the 
base, 3-6 dm. tall : leaf-blades usually erect, long-acuminate, 6--22 cm. long, 2-6 mm. wide: 
panicle linear, 5-15 cm. long, its branches appressed, one-sided : spikelets about 3 mm. long, 
crowded, oval or obovoid, obtuse, turgid, in pairs, the one short- the other long-pedicelled, 
glabrous, the first scale shorter than the rest, 5-nerved. 
In dry usually sandy places, Kansas and Colorado to Texas and Arizona. Alsoin Mexico, Sum- 
mer and fall. : 
3. Panicum mólle Sw. Sterile stems 1-2 m. long, rooting at the nodes, the fertile 
stems erect, 6-10 dm. tall or more, the nodes densely barbed : leaf-sheaths often overlap- 
ping, papillose-hirsute : blades 1-3 dm. long, glabrous or pubescent, 7-15 mm. wide: 
panicle 1.5-2 dm. long, its branches spreading or ascending : spikelets about 3 mm. long, 
glabrous. 
à a, fields and along roadsides, Florida to Texas. Introduced from tropical America. Summer 
and fall. 
4. Panicum paspaloides Pers. Aquatic. Stems 6-12 dm. long, usually clothed with 
sheaths below : leaves glabrous; blades 2.5 dm. long or less, 6-10 mm. wide: racemes 
10-20, one-sided, the rachis broadly winged, appressed, 2-3.5 em. 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. 
In shallow water, southern Florida and Texas. Also in tropical America, Asia and Australia 
Spring to fall. WATER GRASS. 
