GRAMINEAE 13 



Rachilla not extending beyond the palet. 

 Flowering scale awned. 



Flowering scale 3-awned. 17. Aristida. 



Flowering scale i -awned. 

 Awn twisted. 18. Stipa. 



Awn not twisted. 

 Flowering scale narrow : awn persistent. 21 . Muhlenbergia. 

 Flowering scale broad : awn deciduous. 19. Oryzopsis. 



Flowering scale awnless. 20. Milium. 



Rachilla extending beyond the palet. 22. Brachyelytrum. 



B. Flowering scale usually hyaline or membranous at maturity, at least more 

 delicate than the empty ones : grain loosely enclosed. 

 Inflorescence a spike. 

 Rachilla of the spikelets articulated below the empty scales, hence decid- 

 uous entire. 25. Alopecurus. 

 Rachilla of the spikelets articulated above the empty scales which are 

 therefore persistent. 

 Flowering scales slightly exceeding the empty ones. 



23. Heleochloa. 

 Flowering scales much shorter than the empty ones. 



24. Phleum. 

 Inflorescence an open or spike-like panicle. 



Grain not permanently enclosed in the flowering scale and palet : pericarp 



opening readily when mature. 26. Sporobolus. 



Grain permanently enclosed in the flowering scale and palet : pericarp ad- 

 herent. 

 Spikeletsreadily falling off entire when mature. 27. Polypogon. 

 Spikelets with the empty scales at least persistent. 



Palet i-nerved and i-keeled: stamen i. 28. Cinna. 



Palet 2-nerved and 2-keeled : stamens 3. 

 Flowering scale bifid, delicately awned on the back : rachilla pro- 

 longed into a short bristle. 32. Apera. 

 Flowering scale entire : rachilla not prolonged into a bristle. 

 Flowering scales naked at the base. 29. Agrostis. 

 Flowering scale with long hairs at the base. 

 Flowering scale and palet thin-membranous. 



30. Calamagrostis. 

 Flowering scale and palet chartaceous. 



31. Ammophila. 

 Tribe VIII. AVENEAF. 



Spikelets readily deciduous as a whole. 33. Holcus. 



Spikelets with the empty scales persistent, the flowering scales deciduous. 

 Spikelets 2-flowered : rachilla not prolonged. 34. Aira. 



Spikelets 2-many-flowered : rachilla extending beyond the upper flower. 

 A. Flowering scale awned below the teeth, 

 a. Flowers all perfect. 

 Grain free, unfurrowed : spikelets less than i cm. long. 

 Flowering scales erose-toothed or shortly 2-lobed at the apex. 



35. Deschampsia. 

 Flowering scales cleft or 2-toothed, the teeth extending into awns. 



36. Trisetum. 



Grain furrowed, adherent to the scale : spikelets exceeding i cm. in 

 length. 37. Avena. 



