54 POACEAE 
l. Tripsacum dactyloides L. Glabrous, or on the summit of the sheaths and the 
upper surface of the leaves more or less hirsute. Stems 1-2.5 m. tall, from stout root- 
stocks; blades 6 dm. long or less, 1-4 cm. wide: spikes terminating the stem and its 
branches, single, or at the summit of the stem in 2's-4's, 1-3 dm. long, the lower 1-3 
pistillate, the remainder staminate, the margins of the excavations in the pistillate portion 
ciliate, the sinus at the base with long hairs: pistillate spikelets 7-10 mm. long, orbicular- 
ovate: staminate spikelets 7-10 mm. long, 1.5-2 mm. broad, oblong, the outer 2 scales 
glabrous or puberulent. 
In swamps or along streams, Rhode Island to Kansas, Florida, Texas, and Mexico. Summer and 
fall GAMA GRASS. 
2. Tripsacum Floridanum Porter. Similar to the preceding species, but much more 
slender. Stems from stout rootstocks, 6-10 dm. tall: leaf-blades long and narrow, usually 
5-8 mm. wide: spikes rather slender, 1.5-2 dm. long, single, terminal, never axillary. 
In moist or wet places, peninsular Florida and the Keys to Texas. Spring and summer. 
2. IMPERATA Cyr. 
Perennial grasses, with long leaf-blades and long terminal cylindric dense and spike- 
like panicles. Spikelets 1-flowered, rarely 2-flowered, narrow, in pairs, unequally pedicel- 
late. Scales 4, thin, hyaline, awnless, the outer 2 empty, pilose, the third scale glabrous, 
empty or rarely enclosing a palet and staminate flower, the fourth scale glabrous, subtend- 
ing a perfect flower and its 2-nerved palet which is truncate and toothed at the apex. 
Stamens l or 2. Styles distinct. Stigmas plumose. 
1. Imperata Brasiliénsis Trin. Stems tufted, 3-8 dm. tall, slender: leaf-sheaths 
smooth and glabrous ; blades 3 dm. long or less, 3-8 mm. wide, smooth beneath, hirsute 
above near the base: panicle 6-15 cm. long, 1.5-3 cm. broad, oblong, its branches 1.5-4 
cm. long, ascending: spikelets about 4 mm. long, the one about equalling, the other about 
twice as long as its pedicel, the outer 2 scales and the callus densely clothed with hairs, 
these, as well as those at the summit of the rachis internodes, more than twice as long as 
the spikelets. 
In dry soil, southern peninsular Florida. Also in tropical America. Spring and summer. BBRA- 
ZILIAN BLADY-GRASS. 
3. ERIANTHUS Michx. 
Tall perennial grasses, with frequently robust stems arising from thick rootstocks, and 
with flat leaf-blades and perfect flowers in open or contracted terminal panicles. Spikelets 
usually with a basal ring of long hairs, or rarely naked, in pairs at each joint of the artic- 
ulated and often hairy rachis. Scales 4, the outer 2 indurated, frequently hairy, the re- 
mainder hyaline, the fourth scale often 2-toothed at the apex, bearing an awn which is 
straight, spiral, or more or less contorted ; palet small, hyaline. Stamens 3. Styles dis- 
tinct, elongated. Stigmas plumose. PLUME Grass. BEARD GRASS. 
Spikelets with a basal ring of hairs at least 14 its length, the outer 2 scales long- 
pilose or becoming glabrous. 
Panicle pale, rarely tinged with P a the basal hairs much exceeding the 
eco d yellowish white spikelet. 
Exserted portion of the awn loosely coiled, the included part tightly spiral. 1. E. alopecuroides. 
Exserted portion of the awn straight, the included portion rarely slightly ae 
2. E. Tracyi. 
twisted. 
Panicle dark, often tinged with purple, the basal hairs?from'shorter than to ex- 
ceeding the yellowish brown or dark brown spikelet. 
Exserted portion of the awn straight. 
Spikelets 6 mm. long or less, equalling or shorter than the basal hairs. 
Panicle dense and compact, its branches short and erect; basal hairs 
about as long as the spikelet. 3. E. compactus. 
Paniele loose and open, its branches long and ascending ; basal hairs 
much exceeding the spikelet. 
Internodes of the branches commonly about as long as the spikelets 
whieh are about 24 as long as the basal hairs. 4. E. saccharoides. 
Lower internodes of the elongated branches much exceeding the 
: spikelets which are about 14 as long as the basal hairs. 5. E. lazus. 
Spikelets 8 mm. long or more, exceeding the basal hairs. 6. E. brevibarbis. 
Exserted portion of the awn contorted or loosely spiral. 
Spikelets 7.5 mm. long or less; summit of the stem and panicle-axis gla- 
.. brous orsparingly appressed-hirsute. 7. E. contortus. 
Spikelets 8-9 mm. long; summit of the stem and panicle-axis densely ap- 
pressed-hirsute. 8. E. Smallü. 
Spikelet naked at the base or with a few short hairs, the outer 2scales strongly ap- 
pressed-hispid. 9. E. strictus. 
