POACEAE. 



A. Spikelets falling from the pedicel entire (see also no. 22 of section B), naked, or 



enclosed in bristles or sometimes in a bur-like involucre, or immersed in the 

 internodes of a readily disarticulating rachis, 1-flowered, or if 2-flowered the 

 lower flower staminate; no upper empty scales: rachilla not extending beyond 

 the uppermost scale. 

 Spikelets round or somewhat dorsally compressed : empty scales manifest : hilum 



punctiform. 

 Flowering scale and palet hyaline, thin, much more delicate in structure than 



the thick-membranous to coriaceous empty scales. 

 Spikelets unisexual, the pistillate borne in the lower, the staminate in the 



upper, part of the same spike. TRIBE I. MAYDEAE. 



Spikelets in pairs, one sessile, the other 

 pedicellate, the former perfect, the 

 latter sometimes perfect, more com- 

 monly with a staminate flower, often 

 empty or reduced to one or two 

 scales, or occasionally wanting. 

 Flowering scale, at least that of the perfect 

 flower; similar In texture to the empty 

 scales, or frequently thicker and firmer, 

 never hyaline and thin. 



Spikelets much compressed laterally : empty 

 scales none or rudimentary : hilum linear. 



B. Spikelets with the empty scales persistent, the rachilla hence articulated 



them (below them in no. 22 and the spikelet falling from the pedicel entire), 

 1-many-flowered ; frequently the upper scales are empty : rachilla often pro- 

 duced beyond the uppermost scale. 

 Spikelets borne in open or spike-like panicles or racemes, usually upon distinct and 



often long pedicels. 

 Spikelets 1-flowered. 

 Spikelets 2-many-flowered. 



Flowering scales usually shorter than 

 the empty ones, the awn dorsal and 

 usually bent. 



Flowering scales usually longer than 

 the empty ones, the awn terminal 

 and straight, rarely dorsal, some- 

 times wanting. 

 Spikelets in two rows. 



TRIBE II. ANDROPOGONEAE. 



TRIBE III. PAXICEAE. 

 TRIBE IV. ORYZEAE. 



TRIBE V. AGROSTIDEAE. 



TRIBE VI. AVEXEAE. 



TRIBE VII. CHLORIDEAE. 

 TRIBE VIII. FESTUCEAE. 



TRIBE I. 



Fertile spikelets imbedded in the internod 

 rachis. 



MAYDEAE. 



of the thick 



1. TRIPSACUM. 

 TRIBE II. AXDROPOGOXEAE. 



Some or all of the racemes sessile. 2. AXDROPOGOX. 



All of the racemes more or less pedunculate. 



Pedicellate spikelets present and usually staminate. 3. HOLCUS. 



Pedicellate spikelets wanting. 4. SORGHASTRUM. 



TRIBE III. PAXICEAE. 



Spikelets not sunken in the rachis. 

 Spikelets naked, not Involucrate. 

 Empty scales 2. 



Lower empty scale with a thickened ring-like 



callus. 5. PASPALUM. 



Lower empty scale unappendaged. 



Spikelets ovate to orbicular, usually obtuse, 



rarely acute. 6. EBIOCHLOA. 



Spikelets lanceolate, acute or acuminate. 7. SYXTHERISMA. 



Empty scales 3. 



Empty scales awned or awn-pointed. 



Stems erect : leaf-blades long and narrow : 



racemes usually of many spikelets. 9. ECHINOCHLOA. 



Stems creeping : leaf-blades short and broad : 



racemes or clusters usually of few spikelets. 10. OPLISMEXUS. 

 Empty scales not awned. 



Stems and branches not woody nor bamboo-like. 



Fruiting scale rigid, the margins inrolled. 11. PAXICUM. 

 Fruiting scale not rigid, the hyaline mar- 

 gins not inrolled. 



Spikelets In very slender, one-sided, 

 racemes which are usually whorled 

 or approximate. 7. SYXTHERISMA. 



