156 PATAGONIAN EXPEDITIONS I BOTANY. 



d. Bristles persisting after the fall of the spikelets. 



7. Setaria (Ixophorus), p. 164. 

 dz. Spines forming a bur ; falling away with the spikelets. 



8. Cenchrus, p. 165. 

 Az. Spikelets i -flowered, monoecious. Aquatic or marsh-grasses, stamens 6 or more. 



(ORYZEAE.) 



b. Creeping ; male and female flowers in separate panicles. 9. Luziola, p. 165. 



bz. Tall, male and female flowers in the same panicle, the females terminal. 



10. Zizaniopsis, p. 166. 



A^. Spikelets i -many-flowered. When i -flowered, often with prolonged axis; this is jointed 

 above the empty glumes and persists after the fall of the floral glume and flower. When 

 2 -flowered there is an internode between the flowers. 

 B. Culm herbaceous, annual. Leaf-blade continuous with (not articulated on) the leaf-sheath 



and not petioled. 



C. Spikelets on pedicels, in lax or spike-like panicles, or in racemes. Rachis not thick- 

 ened and excavated. 

 D. Spikelets I -flowered. 



e. Glumes 5, the fifth floral. Palea i -nerved. (PHALARIDE^E.) 



f. First glume shorter than second. Third and fourth still shorter, awned 

 dorsally, empty. Stamens 2. 11. Anthoxanthum, p. 166. 



fz. Glumes I and 2 subequal, 3 and 4 nearly as long, often with a male flower, 

 awnless or shortly awned. Stamens in the hermaphrodite flowers 2. 



12. Hierochloe (Savastana), p. 166. 

 /3. Glumes 3 and 4 small and empty, awnless. Stamens 3. 



13. Phalaris, p. 167. 



ez. Empty glumes only 2 (rarely none), equalling or exceeding the floral glume. 

 Palea 2-nerved, grain not grooved. Spikelets stalked. (AGROSTIDEJEJ. 



f. Floral glume hard and close about the ripe grain. Spikelets all fertile. 

 g. Floral glume entire ; its awn 3-parted. 14. Aristida, p. 168. 

 gz. Floral glume entire ; its awn simple. 



h. Lodicules mostly 3. Floral glume and palea becoming hard. Awn 



long, twisted, persisting. 15. Stipa, p. 168. 



hz. As Stipa, but floral glume broad, and its awn very caducous. 



Cespitose, sometimes tall. 16. Oryzopsis, p. 177. 



^3. Lodicules 2, the anterior pair. Spikelet small, at most coriaceous. 

 Awn short, or a mere mucro. 17. Muhlenbergia, p. 178. 



fz. Floral glume not as hard as the empty glumes, loosely or not at all en- 

 closing the ripe grain. 

 g. Stigma small, brush-like, protruding only slightly. Spikelets forming a 



dense or short quasi-spike, the uppermost not sheathed. 

 h. Empty glumes produced into awns, persisting on the axis. Floral 

 glume much shorter, obtuse, awnless, mostly coming away. 



1 8. Phleum, p. 178. 



hz, Spikelets when ripe easily separating as a whole. Lower pair of 

 glumes more or less united ; third or floral glume dorsally awned. 



19. Alopecurus, p. 179. 



