84 GRAMINEAE 



Spikelets sessile or nearly so, in spikes, 1 to several-flowered. 



Spikelets in 1-sided spikes, usually closely imbricated; spikes digitate or racemose 



Tribe VII. Chlobideae. 

 Spikelets sessile on opposite sides of a more or less zigzag jointed channeled rachis, form- 

 ing a terminal spike; leaf-blades bearing at base a more or less well-marked pair of 



auriculate appendages Tribe IX. Hordeae. 



Tribe I. Andropogoneae. Spikelets in pairs (or the terminal in 3 's) on the usually articvdate 

 rachis of a spike-like raceme, one sessile and fertile, the other pediceled and perfect, 

 staminate, neuter or reduced to a rudiment. Glumes more or less indurated. Lemmas 

 smaller than the glumes, hyaline, that of the fertile florot usually awned. 



Spikelets awnless 1. Imperata. 



Spikelets awned. 



Spikelets in pairs, in racemes, these aggregated in a dense infloresconcr. . .3. An'dropogon. 



Spikelets in 3 's, in an open panicle 2. HoLCUs. 



Tribe II. Zoysieae. Spikelets in groups, each group falling as a whole from the axis; glumes 

 firmer than the lemma, the first usually larger than the second; spikelets 1 or 2-flowered, 

 perfect or with staminate spikelets intermixed. Only one genus, Pleuraphis (no. 4), 

 in California. To this tribe belongs the Korean lawn grass (Zoysia pungens Willd.), 



uccasionally cultivated for lawns 4. Pleubaphis. 



Tribe III. Paniceae. Spikelets all alike, the first glume when present, shorter than the floret, 

 the first or lower lemma similar to the glumes in texture, enclosing a staminate flower, 

 or only a palea, or entirely empty, the second or upper lemma and palea indurated, en- 

 closing a perfect flower and persisting as a covering to the fruit. 

 Spikelets not surrounded by bristles. 



Fruit cartilaginous-indurated, the margins of the lemma not inroUed; inflorescence of 

 slender, more or less digitate, spike-like racemes; our species annual... 5. Diuit.ibia. 

 Fruit indurated, the margins inrolled; inflorescence paniculate or spike-like, not digitate 

 in our species. 



Spikelets plano-convex, imbricated in spike-like racemes 6. P.4SP.\I.UM. 



Spikelets not conspicuously planoconvex. 



Fertile palea included at tip; fruit not pointed; inflorescence paniculate. .7. Panicum. 



Fertile palea free at tip; fruit pointed; spikelets in racemes, these in panicles 



8. ECHINOCULOA 



Spikelets subtemled or surrounded by bristles (sterile branchlets) 9. Set.\bi.\. 



Tribe IV. Phalarideae. Spikelets with 1 terminal perfect floret and a pair of sterile florets 

 below, the group articulated above the glumes and falling entire; sterile florets sometimes 

 staminate, but usually small, or reduced to mere rudiments or pedicels. 

 Glumes strongly compressed, boat-shaped; sterile lenmias empty, narrow, bristle-form or 



scale-like, much shorter than the indurated fertile lemma 10. Phalabis. 



Glumes not strongly compressed or boat-shaped ; sterile lemmas ovate or oblong, longer 

 than the fertile lemma. 



Sterile lemmas, empty, dorsally awned; inflorescence spike-like 11. Anthoxanthum. 



Sterile florets staminate; inflorescence a somewhat open panicle 12. Hieeochloe. 



Tribe V. Agrostideae. Spikelets 1-flowered, the raehilla sometimes prolonged behind the 

 palea as a naked or pUmiose bristle; glumes usually as long as or longer than the lemma. 

 Lemma indurated, usually long-awned. a well marked cnllus at base. 



Awn trifid 13. Aristida. 



Awn simple. 



Awn geniculate and twisted, usually more than i^ inch long 14. Stipa. 



Awn straight or curved, less than li iuch long 15. Obyzopsis. 



Lemma membranaceous (rather firm in Muhlenbergia), usually more delicate than the 

 glumes. 



Inflorescence a flat-topped head, subtended by 2 inflated sheaths 17. Cbypsis. 



Inflorescence sometimes capitate but not flat-topped. 



Lemma awned or mucronate from the tip 16. Muhlenbergia. 



Lemma awnless or dorsally awned. 



Glumes conspicuously compressed-carinate; spikelets in dejise spike-like panicles. 



Lemma awnless ; glumes abruptly aristate 18. Phleum. 



Lemma awned below the middle; glumes not aristate 19. Alopecurus. 



