MANUAL OF THE GRASSES OF THE UNITED STATES 



783 



firm, somewhat coriaceous, dorsally flattened, the margins inflexed around the 

 second glume, a line of balsam glands on the marginal nerves, the apex entire 

 and acute or acuminate, or bifid with aristate teeth; second glume similar 

 to the first; sterile and fertile lemmas thin and hyaline; palea obsolete. Erect, 

 moderately tall perennials, with solitary spikelike, often woolly racemes. 

 Type species, Elyonurus tripsacoides . Name from Greek eluein, to roll, and 

 oura, tail, alluding to the cylindric inflorescence. 



The species are important grazing grasses in the savannas and plains 

 of tropical America, but they extend only a short distance into the United 

 States. 



Rhizomes wanting; culms hirsute below the nodes; racemes conspicuously woolly. 



1. E. BARBICULMIS. 



Rhizomes present; culms glabrous; racemes slightly pubescent, the first glume glabrous or 

 nearly so on the back 2. E. tripsacoides. 



1. Elyonurus barbiculmis Hack. 

 (Fig. 1185.) Culms tufted, erect, 

 simple or sparingly branching, 40 to 

 60 cm. tall, pubescent below the 

 nodes; blades involute, striate, about 



1 mm. thick, the upper surface 

 usually long-pilose; raceme mostly 5 

 to 10 cm. long, pale; rachis joints, 

 pedicels, and spikelets densely woolly, 

 the spikelets 6 to 8 mm. long; first 

 glume acuminate. % — Mesas, 

 rocky hills, and canyons, western 

 Texas to southern Arizona; northern 

 Mexico. 



2. Elyonurus tripsacoides Humb. 

 and Bonpl. ex Willd. (Fig. 1186.) 

 Culms 60 to 120 cm. tall, glabrous, 

 rather freely branching and with 

 short rhizomes; blades flat or involute, 



2 to 4 mm. wide, slightly pilose on 

 the upper surface near the base; 

 raceme 7 to 15 cm. long; rachis 

 joints ciliate, the pedicels pilose; 

 spikelets 6 to 8 mm. long, the first 

 glume ciliate toward the acuminate 

 2-toothed apex, usually glabrous on 

 the back. % — Moist pine woods 

 and low prairies, Georgia, Florida, 

 southern Mississippi, and southern 

 Texas; Mexico to Argentina. 



Figure 1185. 



-Elyonurus barbiculmis, X 1. (Type 

 coll.) 



162. ROTTBOELLIA L. f. 



Spikelets awnless, in pairs at the 

 nodes of a thickened articulate rachis, 

 one sessile and perfect, the other 

 pedicellate, sterile; rachis joints hol- 

 low above, the thickened pedicel 

 adnate to it, the pedicellate spikelet 

 appearing to be sessile; sessile spike- 



let fitting closely against the concave 

 side of the rachis joint, the first 

 glume coriaceous, the second less 

 coriaceous; sterile and fertile lemmas 

 and palea hyaline. Coarse branching 

 annual, with broad flat blades and 

 subcylindric racemes, dwindling to- 

 ward the summit and bearing abor- 

 tive spikelets only. Type species, 

 Rottboeilia exaltata. Named for C. F. 

 Rottboell. 



1. Rottboeilia exaltata L. f. (Fig. 

 1187.) Culms robust, 1 to 3 m. tall, 

 branching; sheaths papillose-hispid, 

 especially toward the summit; blades 

 flat, in robust specimens as much as 

 3 cm. wide; racemes mostly 8 to 12 

 cm. long, 3 to 4 mm. thick, dwindling 

 at the summit; sessile spikelet 5 to 



