XX GENERA. 



often very difficult to distinguish the additional radiment, hut these may he known from all 

 other Em-cpean Grasses not included in the preceding section hy the spikelets in twos or threes, 

 and one of them sessile.] 



a. Spikelets in twos, sessile and stalked ; the latter barren. 



841 . SORGHUM. Spikelets oblong or rather ovoid. Glumes of fertile Fl. coriaceous, 

 without strite. Seed large, roundish, p. 395. 



840. AWDROPOGrOir. Spikelets lineari-lanceolate. Seed nearly linear. In the Euro- 

 j)ean species of this gemis, except in A. Gryllus and A. Allionii, the Fl. are in fingered 

 spikes, p. 395. 



b. Spikelets all fertile, sessile and stalked, in two rows, on one side of a flattened rachis. 



842. DIG-ITAE.IA. Spikes fingered. Spikelets unarmed. Seed invested with the hard- 

 ened pales, p. 396. 



844. OPLISMENUS. Spikes in racemes or panicles. Spikelets naked. Glumes keeled, 

 plaited, or setigerous. p. 396. 



c. Spikelets all fertile, in a compound spike, tiled all round, with a hristle-like involucrum. 



845. SETARIA. Spikelets accompanied by setiform bracts, p. 396. 



846. PEUIflSETUM. Spikelets accompanied hy bracts, some of which are feathery, 

 p. 397. 



d. Spikelets all fertile, disposed in sets, one sessile and one or two stalked, enveloped in long 



silky hairs. 



837. SACCHAmrM. Awnless. Squamules 2. Pales without hairs ; inner minute or 

 wanting. Pan. not spike-Uke. p. 395. 



839. EKIAWTHUS. Lower Pale of fertile Mt. awned. Squamules 2. Sta. 2-3. Pan. 

 spreading, p. 395. 



838. IMPEEATA. Awnless. Squamule 0. Pan. spike-like. p. 395. 



e. Spikelets all fertile, scattered, not enveloped in hairs. 

 851. PHALARIS. Additional Scales short, unarmed. Glumes boat-like, keeled, inclosing 

 Pales, coriaceous, hardening on seed. p. 397. 



850. EHRHABTA. Glumes membranous, unarmed, not inclosing the pales. Barren 

 Fits. 2, coriaceous, transversely wrinkled, inclosing papery pales, p. 397. 



843. PAWICUM. Barren Pit. 1, large, glume-like, embracing the horny, ribless pale. 

 Glumes not inclosing, p. 396. 



ill. Spikelets one- or more flowered, without additional external scales, sessile or nearly so, in 



two rows on one side of a flattened rachis. 

 [In this and aU the following divisions, all the spikelets are perfect, except in Lappago, where 

 the uppei-most of each short spike are barren or neuter, and in Cynosurus, where the barren 

 spikelets form a sort of involucrum.] 



875. CYWODON. Spikelets 1-flowered, with an interior rudiment. Spikes fingered. 

 Glumes unequal, membranous. Pales membranous ; outer broad, embracing the inner. Seed 

 invested with the hardened pales, p. 402. 



876. DACTYLOCTEKTIUM. Spikelets 2- or more flowered. Spikes fingered. Inner 

 Glume mucronate. Pales unequal : the outer ventricose, membranous ; inner scariose. p. 402. 



878. LEPTOCHLOA. Spikelets 2- or more flowered. Spikes in a raceme. Glumes 

 keeled. Outer Pale keeled, 3-nerved. Awn straight, p. 402. 



877. BECKMANNIA. Spikes in a raceme. Spikelets unarmed, 1-2-flowered. Glumes 



