760 MISC. PUBLICATION 200, U. S. DEPT. OF AGRICULTURE 



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. 1680, A.) 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. (Fig. 

 1680, B.) 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, usu- 

 ally glabrous on the back. % — Moist pine woods and 

 low prairies, Georgia, Florida, southern Mississippi, and 

 southern Texas; Mexico to Argentina. 



153. EOTTBOELLIA L. f. 



Spikelets awnless, in pairs at the nodes of a thickened 

 articulate rachis, one sessile and perfect, the other 

 pedicellate, sterile; rachis joints hollow above, the thick- 

 ened pedicel adnate to it, the pedicellate spikelet appear- 

 ing to be sessile; sessile spikelet 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 abortive spikelets only. Type 

 ¥l RMboeUia S exrt- species, Rottboellia exaltata. Named for C. F. Rot'tboell. 

 S'jamaiSf l ' Rottboellia exaltata L. f . (Fig. 1681.) Culms robust, 

 1 to 3 m tall, branching; sheaths papillose-hispid, especi- 

 ally 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, dwind- 

 ling at the summit; sessile spikelet 5 to 7 mm long; first glume finely 

 papillose; pedicellate spikelet about as long as the sessile one. o 

 (Manisuris exaltata Kuntze.) — Introduced at Miami, Fla.; West 

 Indies; native of tropical Asia. The fragile hairs of the sheaths are 

 irritating to the skin of persons handling the plant. 



154. MANIStJRIS L. 



Spikelets awnless, in pairs at the nodes of a thickened articulate 

 rachis, one sessile and perfect, the other pedicellate, rudimentary 

 (developed but sterile in M. altissima), the pedicel thickened and 



