228 



COMPARATIVE ANALYSIS. 



2. Flowers in unilateral spikes . . .3 

 Flowers not unilateral ... 6 



3. Calyx many-flowered . . . Triticum. 

 Calyx one or two-flowered ... 4 



4. Styles united half way up . . . Spartina. 

 Styles distinct .... 5 



5. Glumes nearly equal . . . Cynodon. 

 Glumes very unequal .... Digitaria. 



6. Spikelets imbedded in the rachis . . Rottlolia. 

 Spikelets not imbedded. ... 7 



7. Spikelets two or more from same point . .11 

 Spikelets solitary .... 8 



8. Spikelets one-flowered . . . Knappia. 

 Spikelets more than two-flowered . . 9 



9 . Glume solitary, inclosing the spikelet between it and rachis Lolimn. 

 Glumes two, their edges towards the rachis . .10 



10. Florets equal . . . Br achy podium. 

 Florets smaller upwards . . . Triticum. 



11. Spikelets one-flowered .... Hordeum. 

 Spikelets two or more flowered . . . Elymus. 



12. Calyx one-flowered . . . . 13 

 Calyx two or more flowered . . .23 



13. Glumes with feathery awns . . . Lagurus. 

 Glumes awnless, or awns not feathery . 14 



14. Panicle dense, (subspiked,) florets mostly imbricated . 15 

 Panicle loose, florets not imbricated . . 20 



15. Corolla with tuft of hair at base . . AmophiUa. 

 Corolla without hairs at base . . . 16 



16. Corolla with one or two valves of imperfect florets at base Pkalaris. 

 Corolla without valves of imperfect florets at base . 17 



17. Corolla awnless ..... Plileum. 

 Corolla awned . . . . 18 



18. Corolla of one valve, the awn basal . . Alopecurm. 

 Corolla of two valves, the awn terminal or dorsal . 19 



19. Glumes awned, awn of corolla terminal . Polypogon. 

 Glumes awnless, awn of corolla dorsal . . Gastridium. 



20. Fruit inverted with the hardened corolla; corolla awnless 21 

 Fruit not inverted with the corolla; corolla often awned 22 



21. Corolla with a small valve at the base . Phalaris. 

 Corolla without a valve at the base . . Mil in in. 



22. Corolla with long hairs at base . . Calamagrostis. 

 Corolla without hairs at base . . . Agrostis. 



23. Florets with a pinnated bractea . . Cynosurm. 



