Part 2, 1912] POACEAE 127 
7-nerved, with the keels hispid above, otherwise glabrous, the intercarinal space depressed 
in the center and sometimes with a deep pit-like depression above the middle, the second 
scale equaling the first, 3-nerved, the awn of the fourth scale perfect, 1.5-2 cm. long, the column 
often geniculate or curved, much exserted; pedicellate spikelet usually reduced to a single 
scale about 3 mm. long. 
TYPE LOCALITY: Orizaba, Vera Cruz, 
DISTRIBUTION : Known only from the type locality, 
9. Amphilophis piptatherus (Hack.) Nash. 
Andropogon piptatherus Hack. in Mart. Fl. Bras, 23: 293. 1883. 
Andropogon piptatherus Palmeri Hack. in DC. Monog,. Phan. 6: 580. 1889. 
Sorgum piptatherum Kuntze, Rev. Gen. 792. 1891. 
Annual. Stems 3-10 dm. tall, barbed at the nodes, branched; leaf-sheaths glabrous or 
pubescent toward the apex; blades up to 2.5 dm. long, 3-10 mm. wide, lax, usually rough, 
often pubescent; racemes numerous and in a corymbiform panicle 2-3 cm. long, or in 2’s—10’s, 
rarely solitary, on peduncles 5-20 mm. long, lax, the internodes of the rachis and pedicels 
shorter than the sessile spikelets, flat, much compressed, ciliate on the thickened margins, 
with a broad median hyaline line; sessile spikelet 3-4 mm. long, the first scale membranous, 
oblong, very obtuse, ciliate on the keels, 5-7-nerved, pilose below on the back, the second scale 
equaling the first, keeled, glabrous; fourth scale with an awn 2.5-3.5 cm. long; pedicellate 
spikelet empty, 5~6 mm. long, lanceolate-oblong, the first scale flat, 12-17-nerved, pilose below. 
TYPE LOCALITY: Porto Imperial, Goyaz, Brazil. 
DISTRIBUTION: Central and southern Mexico; also in tropical South America and Africa. 
24. HETEROPOGON Pers. Syn. Pl. 2: 533. 1807. 
Annual or perennial grasses, sometimes tall, with narrow leaf-blades, and spike-like racemes 
borne singly at the apex of the stem and its branches, the lower pairs of spikelets differing 
from those above in sex and awns. Spikelets 1-flowered, in pairs at the rachis-nodes, one 
sessile, staminate or empty in the lower pair or pairs, pistillate or perfect in the remaining pairs, 
the other pedicellate, containing a staminate flower, or empty. Sessile spikelet of 4 scales; 
first scale firm, convolute, awnless; second scale thinner, keeled; third scale very thin, hyaline; 
fourth scale enclosing the flower, small and hyaline, bearing a long rigid contorted perfect 
awn. Pedicellate spikelet awnless, differing much in appearance from the perfect sessile 
spikelet, not convolute. Stamens 3. Styles distinct. Stigmas plumose. 
Type species, Andropogon Allionit DC. 
Upper sheaths along the keel and the first scale of the pedicellate spike- 
let on the midnerve tuberculate, the latter 1.5 cm. long or more, glabrous. 1. HY. melanocarpus. 
Upper sheaths and the first scale of the pedicéllate spikelet smooth, the latter 
lem. long or less, papillose-hispid toward the summit and near the 
margins. 2. Hl. contortus. 
1. Heteropogon melanocarpus (Muhl.) Ell.; Benth. Jour. 
Linn. Soe. 19: 71. 1881. 
Stipa melanocarpa Muhl. Cat. 13. 1813; Descr. Gram. 183. 1817. 
Andropogon melanocarpus Ell. Bot. S. C. & Ga. 1: 146. 1816. 
Cymbopogon melanocarpus Spreng. Syst. 1: 289. 1825. 
Trachypogon scrobiculatus Nees, Agrost. Bras. 347. 1829. 
Heteropogon acuminatus Trin. Mém. Acad. St. Petersb. VI. 2:.254, 1832. 
Andropogon scrobiculatus Kunth, Enum. 1: 507. 1833. 
Heteropogon scrobiculaius Fourn. Mex. Pl. Gram. 64. 1881. 
Sorgum melanocarpum Kuntze, Rev. Gen. 792. 1891. 
Annual. Stems 4-15 dm. tall, much branched above; leaf-sheaths, at least the upper 
ones, tuberculate on the keel; blades 5 dm. long or less, 3-12 mm. wide; racemes 3-6 cm. 
Jong, exserted, or included at the base, the peduncles pilos¢ with ascending hairs, the internodes 
between the upper spikelets densely pubescent with long chestnut-brown hairs; pistillate sessile 
spikelet 5-6 mm. long, the awn 9-15 cm. long; pedicellate spikelet 1.5-2.5 cm. long, empty 
or staminate, the first scale long-acuminate, tuberculate on the midnerve. 
TYPE LOCALITY: Georgia. . : . ; . . 
DISTRIBUTION: South Carolina to Florida, Arizona, and Mexico, and in tropical America. 
ILLUSTRATION : Bull. U. S. Dep. Agr. Agrost. 17: 7. 323. 
