GENERA OF GRASSES OF THE UNITED STATES. 187 



Perennial or rarely annual grasses, with short, flat, stiff blades, 

 numerous stiff, slender, divergent spikes loosely scattered along the 

 upper part of the culm, or sometimes aggregate toward the summit, 

 the spikes often deflexed at maturity. Species 10, nearly all Amer- 

 ican ; 3 species in the southeastern United States. 



Type species : Andropogon ambiguus Michx. 



Gymnopogon Beauv., Ess. Agrost. 41, pi. 9, f. 3. 1812. Beauvois mentions one 

 species, Andropogon ambiguus Michx., which is figured. In the description of 

 the plate the name given is Gymnopogon, raceinosus. 



Alloiatheros Ell., Bot. S. C. and Ga. 1: 146. 1816. This name is casually 

 mentioned by Elliott in the description of Andropogon ambiguus: "I once in- 

 tended to insert it as a distinct genus under the name of Alloiatheros, from the 

 dissimilarity of its awns, not only in position but in figure." 



Anthopogon Nutt, Gen. PI. 1: 81. 1818. Based on Andropogon ambiguus 

 Michx., which name Nuttall changes to Anthopogon lepturoides. 



The spikelets are usually 1-flowered and awned,but in G-ymnopogon 

 chapmanianus Hitchc., of Florida, they are 2 to 4 flowered and awn- 

 less. This species shows in its spikelet characters a transition to 

 Leptochloa, but in habit it closely resembles the other two species of 

 the United States. In G. foliosm (Willd.) Nees, of Porto Eico and 

 South America, the rudiment bears two long awns. Our species are 

 perennials, with an inflorescence of scattered spikes. 



Our commonest species is Gymnopogon ambiguus (Michx.) B. S. P. 

 (fig. Ill) , found in sandy soil from New Jersey to Missouri and south 

 to Florida and Texas. Another species, G. l>revifolius Trin., grows 

 from New Jersey to Florida. This species differs from the preced- 

 ing in having the rachis spikelet bearing only along the upper half . 

 The species have no agricultural importance. 



93. CHLOBIS Swartz. 



Spikelets with 1 perfect floret, sessile, in two rows along one 

 side of a continuous rachis, the rachilla disarticulating above the 

 glumes, produced beyond the perfect floret and bearing 1 to several 

 reduced florets consisting of empty lemmas, these often truncate, and, 

 if more than one, the smaller ones inclosed in the lower, forming a 

 usually club-shaped rudiment; glumes somewhat unequal, the first 

 shorter, narrow, acute; lemma keeled, usually broad, 1 to 5 nerved, 

 often villous on the callus and villous or long-ciliate on the keel or 

 marginal nerves, awned from between the short teeth of a bifid apex, 

 the awn slender or sometimes reduced to a mucro, the sterile lemmas 

 awned or awnless. 



Perennial or sometimes annual, tufted grasses, with flat blades and 

 two to several often showy and feathery spikes aggregate at the 

 summit of the culms. Species about 60, in the warmer regions ; 15 in 

 the southern United States. 



Type species : Agrostis cruciata L. 



Chloris Swartz, Prod. Veg. Ind. Occ. 25. 1788. Swartz describes five species, 

 C, cruciata, C. ciliata, C. petraea, C. polydactyla, and C. radiata, all from the 



