68 POACEAE 



fourth scale, enclosing a pistillate flower, small and hyaline and bearing a long rigid con- 

 torted and geniculate awn ; palet small and hyaline, or wanting. Pedicellate spikelet awn- 

 less, the outermost scale thinner than the corresponding one in the sessile spikelet. Sta- 

 mens 3. Styles distinct. Stigmas plumose. 

 Upper sheaths tuberculate along the keel and the first scale of the pedicellate 



spikelet on the midnerve, the latter 1.5 cm. long or more and glabrous. 1. H. mclanocarpu*. 



Upper sheaths and the first scale of the pedicellate spikelet smooth all over, the 

 latter 1 cm. long or less, papillose-hispid toward the summit and near the 

 margins. 2. H. contort us. 



1. Heteropogon melanocarpus (Muhl. ) Ell. Annual. Stems 4-15 dm. tall, much 

 branched above : upper leaf-sheaths at least tuberculate on the keel ; blades 5 dm. long or 

 less, 3-12 mm. wide : racemes 3-6 cm. long, exserted, or included at the base, the pedun- 

 cles pilose with ascending hairs, the internodes between the upper spikelets densely pu- 

 bescent with long chestnut-brown hairs : sessile spikelet 5-6 mm. long, the awn 9-15 cm. 

 long ; pedicellate spikelet 15-22 mm. long, sterile or staminate, the first scale long-acumi- 

 nate, tuberculate on the midnerve. [ H. acuminatus Trin. ] 



In cultivated grounds. South Carolina to Florida, Texas, Arizona and Mexico. Also in tropical 

 America. Summer and fall. 



2. Heteropogon cont<5rtus (L. ) Beauv. Perennial. Stems 2-8 dm. tall, rather 

 sparingly branched above : leaf-sheaths smooth, even on the keel ; blades 2 dm. long or 

 less, 3-7 mm. wide : racemes 4-6 cm. long, exserted, or included at the base, the peduncles 

 hispidulous, the internodes between the upper spikelets densely pubescent with long nearly 

 appressed chestnut-brown hairs : sessile spikelet 5-6 mrn. long, the awn 4.5-8 cm. long ; 

 pedicellate spikelet about 1 cm. long, sterile or staminate, the first scale acute, papillose- 

 hispid toward the summit and near the margins with long hairs. 



In dry soil, southern and western Texas to Arizona and Mexico. Widely distributed in the warmer 

 parts of all countries. Spring to fall. 



16. HILARIA H.B.K. 



Stoloniferous grasses, decumbent and branching at the base, with flat or convolute 

 leaf-blades and spicate inflorescence. Spiklets in sessile deciduous crowded clusters of 3, 

 the empty scales resembling an involucre, the central spikelet 1 -flowered, the flower pistil- 

 late or perfect, the lateral spikelets 2-flowered, the flowers staminate. Scales 4, the 2 outer 

 empty, rigid, thin or indurated, the first the larger and varying much in shape, entire 

 or 2-cleft at the toothed or lacerate apex, awnless, or bearing an awn between the lobes, 

 the second scale narrower, often keeled, entire or 2-toothed at the apex, awnless, mucronate, 

 or short-awned ; third and fourth scales thin-membranous, entire or toothed at the apex, 

 each in the lateral spikelets enclosing a palet and a flower, in the central spikelet the third 

 scale is empty. Stamens 3. Styles a little united at the base. Stigmas shortly plumose. 

 Outer scales of the spikelet linear or oblong, the nerves parallel, some of them awned. 1. H. Texana. 

 Outer scales of the spikelet cuneate, the nerves strongly diverging above, awnless. 2. H. mutica. 



1. Hilaria Texana (Vasey) Nash. Creeping by arched stolons. Stems 1-2.5 dm. 

 tall : basal leaves numerous ; blades 1-5 cm. long and about 2 mm. wide, very rough, pu- 

 bescent, the upper surface densely so with short hairs, the lower surface with a few long 

 hairs : spike 2-3 cm. long, of 4-8 spikelets, which are 4-5.5 mm. long, each cluster naked 

 at the base. 



On hills and plains, central Texas to Arizona. Spring and summer. CREEPING MESQUITE. 



2. Hilaria mutica (Buckl. ) Benth. Stems rigid, 2-6 dm. tall, from rootstocks : leaf- 

 blades erect, firm, 1 dm. long or less, 2-4 mm. wide : spike 4-6 cm. long : spikelets many, 

 crowded, usually overlapping, 6-7 mm. long. 



On plains and prairies, Texas to Arizona. Also in Mexico. Summer and fall. BLACK GRAMA. 



17. NAZIA Adans. 



An annual grass, with flat leaf -blades and racemose or spike-like inflorescence. Spikelets 

 articulated below the empty scales, 1-flowered, solitary, or in clusters of 3-5. Scales 2 or 3, 

 the first small, or sometimes wanting, the second firm, with its nerves dorsally armed with 

 hooked prickles, the third scale membranous, subtending a hyaline palet and a perfect 

 flower. Stamens 3. Styles short, distinct. Stigmas moderately long, plumose. 



1. Nazia aliena (Spreng.) Scribn. Tufted. Stems finally prostrate and rooting and 

 branching at the lower nodes. 1-3 dm. tall : leaf-blades ciliate on the margin : spike 4-10 

 cm. long : spikelets about 2.5 mm. long. 



On dry hillsides, Texas to Arizona. Also in Central and South America, and the West Indies. 

 Spring and fall. 



