62 PAXicACE.ii;. 



linear, truncate, mucronate, 3-keele(i, convex on tlie back, 3-nerved; 

 third shorter, nerveless, fourth a little sliortcr, linear, entire or 

 with two short lobes, 1-nerved, the awn 12-15 cm. long, flexuose, 

 scabrid, stout, 10-15 cm. long; palea 0. Anthers 1.5 mm. long. 

 Pedicellate sj^ikelets on scabrid pedicels as long as the sessile 

 spikelet, first glume subulate, 3-nerved. 



Florida, Chapman, Garher, Curtiss 30-44*. 



Subgenus 7. Dichaxthium Hack. D. C. Monog. Phan. : oGO 

 (18S0). Dirlianthium Willem, in Usteri Ann. liot. IS : 11 (1?!)(;). 



Racemes digitate or rarely solitary, terminal or lateral, forming 

 a true ))anicle. the lower fourtli of the racemes homagamous. The 

 perfect spikolets obcom[)ressed, awued; first glume keeled above, 

 second keeled, awnless, third hyaline, fourth very narrow, bearing 

 a short awn at the tip or between the teeth. Grain eompi'essed, 

 flat in front, convex on the back; embryo a half to two-thirds the 

 length of the grain; pedicellate spikelets staminateor rarely neuter. 



Perennials, excepting A. pipfafhenis, with fiat leaf-blades. 

 Culms rarely branching; panicle more or less exserted, the ho- 

 mogamous part persistent, the rest deciduous. Found in tropical 

 regions. 



,30. A. piptatherus Hack. Mart. Fl. Bras. 3 ; part 3,203 (1883). 



Var. Palmeri Hack. D. C. Monog. Phan. C : 580 (1880). 



Annual; culms erect, slender, terete, .30-40 cm. high, most of 

 the bearded nodes bearing 1 or 2 c<mii)ound branches. Sheaths 

 loose, compressed, thinly pilose; ligule short, obtuse: blades thin, 

 narrow at the base, 8-25 cm. long, 3-10 mm. wide, nu)re or less 

 pubescent with tubercled hairs. Kacemes usually corymbose, pedi- 

 cels very smooth, barbellate in the axils, 2.5-5 cm. long. Fertile 

 spikelets 4 mm. long, linear-oblong, first glume firm, obtuse mar- 

 gins involute. 5-7-uerved, pilose on the lower third or half; second 

 as long as the first, keeled, 3-nerved, irlabrous; fourth bearing an 

 awn 2.5-3.5 cm. long. Anthers 0.5-1 mm. long. Pedicellate 

 spikelets weut( ., consisting of two glumes. 



Mexico, Pahncr '>'M, Prinijh' MWl. 



Subgenus 8. Hktkhoi'Ooon Hack. D. C. Monog. Phan. (5 : 

 683 (1880). ITetoropoijim (genus) Pers. Syu. 2 : 533 (1807). 



