366 WEEDS AND USEFUL PLANTS. 



Spikelets with more than one of the lower flowers perfect. 

 Spikes digitate at the summit of the culm, dense. Glumes 

 and palese both awnless and blunt. 10. 



4. Spikelets several- (few to many-) flowered, often with the upper- 

 most (rarely the lowest) floret imperfect or abortive, usually 

 disposed in open panicles. Palese pointless or the lower one some- 

 times tipped with a straight awn or bristle. Stamens 1-3. 

 * Culms herbaceous. Lower flowers of the spikelets all perfect. 

 Grain free from the palese and smooth. 



Glumes (rather long) and the lower palea awn-pointed, 

 herbaceous, compressed-keeled. Panicle contracted in 

 one-sided clusters. 11. DACTYLIS. 



Lower palea awnless and pointless. 



Lower palea rounded on the back, 5- 7-nerved, scarious 

 at the tip. Spikelets many-flowered, the rachis com- 

 monly breaking up into joints at maturity. 12. GLYCERIA. 

 Lower palea laterally compressed, mostly keeled, mem- 

 branaceous, 5-nerved, the margins or nerves below 

 often cobwebby-pubescent. Spikelets flattened. 13. POA. 

 Lower palea convex on the back, acute, sub-coriaceous, 



3 -5-nerved, not cobwebby at base. 14. FESTUCA. 



Grain adherent to the upper palea and hairy at the apex. 



Lower palea convex or keeled on the back, mostly awned 



below the 2-cleft tip, 5-9 nerved. 15. BROMUS. 



** Culms herbaceous, often tall and reed-like. Lowest flower sterile. 

 Spikelets strongly silky-bearded on the rachis, loosely 



flowered. 16. PHRAGNITES. 



*** Culms woody, suffruticose or arborescent. 



Spikelets flattened, loosely 5 - 14-flowered. 17. ARU.YDI.VARIA. 



^ 5. Spikelets 1 -several-flowered, sessile on opposite sides of a zigzag 

 jointed rachis (which is toothed or excavated on one side of each 

 joint), forming a spike. Glumes sometimes abortive or wanting. 

 Otherwise as in 4. 

 Spikelets single at each joint of the rachis ; several-flowered. 



Glume 1, external. Spikelets placed edgewise on the rachis. 18. LOMUM. 

 Glumes 2, transverse (right and left) ; spikelets placed flat- 

 wise on the rachis. 



Spikelets 3 -several-flowered. 19. TRITICUM. 



Spikelets 2-flowered. 20. SECALE. 



Spikelets 2-4 at each joint of the rachis. 



Spikelets 1-flowered, 3 at each joint, the 2 lateral ones usually 



sterile. 21. HORDEUM. 



6. Spikelets 2-several-flowered,panicled ; the rachis or base of the 

 flowers often villous-bearded. Glumes mostly equalling or exceed- 

 ing the flowers. Lower palea mostly bearing a twisted, bent or 

 straight awn on its back below its apex. Stamens 3. 

 Flowers all perfect, or the uppermost merely rudimentary. 

 Lower palea cleft at the apex into 2 acute teeth. 

 Awn proceeding from the mid-nerve only, below the apex, 



mostly twisted or bent. Lower palea rounded on the back. 22. AVEXA. 

 One of the flowers staminate only. 



Lower flower staminate ; the perfect one commonly awnless; 



the uppermost a rudiment. Otherwise as in 22. 23. ARRHESATHERUM. 



Lower flower perfect and awnless ; the upper staminate and 

 awned. Rudiment none. 24. HOLCUS. 



2. THE PHALARIS SUB-TRIBE. 



Spikelets more or less panicled, 3-flowered, the uppermost or middle 

 flower perfect ; those (apparently) on each side imperfect, staminate, 

 neutral or reduced to an inconspicuous rudiment. 



Lateral flowers neutral, each of a single awned palea, the per- 

 fect flower awnless with 2 stamens. 25. ANTHOXANTHUM. 

 Lateral flowers reduced to a small rudiment on each side of the 

 coriaceous, shining, flattened fertile one 26. PHALARIS. 



