BOTANY. 69 



rachis, forming a solitary spike. Glumes horizontal, often side by side in the 

 same plane, sometimes deficient. Pale?e, either pointless or the lower some- 

 times tipped with a straight aAvn or bristle. 



The principal genera are Hordeum, Secale, Triticura. Hordeum vulgare 

 and disticum constitute common barley. Rye is Secale cereale, and the com- 

 mon wheat is Triticum vulgare. 



Tribe 4. Festiicacece. Spikelets several- (few- or many-) floAvered, panicled, 

 the uppermost flower often imperfect or abortive. Palcfe pointless, or the 

 lower sometimes tipped with a straight (not twisted nor deeply dorsal) awn or 

 bristle. Stamens one to three. Squamulie two. 



The common cheat, or chess, Bromus secahnus, belongs to this tribe. 

 Also, the orchard-grass, Dactylis glomerata ; Rattlesnake-grass, Glyceria 

 canadensis : meadow or spear grass, Poa annua and pratensis ; Blue grass, 

 or Wire grass, Poa compressa. False red-top grass, Poa serotina ; Fescue 

 grass, Festuca elatior and pratensis. The bamboo, Bambusa arundinacea, is 

 represented mpl. 55, ßg. 10. 



Tribe 5. Avejiacea;. Spikelets two, several-flowered, panicled, the terminal 

 flower mostly imperfect. Glumes and paleae, thin and membranaceous, or 

 chartaceous, the lower palea bearing a twisted or bent awn on the back. Sta- 

 mens three. SquamuliB two. 



The common oat, Avena sativa, the skinless oat, A. nuda, and the Hair- 

 grass, Aira csespitosa and flexuosa, belong to this tribe. 



Tribe 6. Chloridea. Spikelets (rarely one-flowered) usually several-flowered, 

 with the upper flowers imperfect, disposed in one-sided spikes. Glumes per- 

 sistent, the upper one looking outward. Rachis or axis jointless. Spikes 

 usually racemed or digitate. Stamens two or three. 



Here belong the Cord grass, Spartina cynosuroides, and other well-known 

 species of Spartina ; the crab grass, Eleusine indica, and the Bermuda grass, 

 Cynodon dactylon. 



Tribe 7. Papjwphorecc. Spikelets two, many-flowered. Superior flowers 

 abortive. Two glumes and two palefe. membranaceo-hcrbaceous. Lower palea, 

 three, meltifid, the divisions subulate awned. The principal genera are Am- 

 phipogon, Diplopogon, Triraphis, Pappophorum, Cottea, &c. 



Tribe 8. ArundinacecE. Spikelets sometimes unifloral with or without 

 the pedicel of a superior flower, sometimes multifloral. Flowers most 

 frequently covered or surrounded at their base with long, soft hairs, two 

 glumes and two membranaceo-herbaceous palefe, the glumes often equal or 

 superior to the flowers in length, the inferior palea aAvned or pointless. 

 Plants genei-ally elevated. 



Tribe 9. Agrostidea-.. Spikelets flowered, perfect, sometimes with the 

 abortive pedicel or rudiment of a second flower above, panicled, or the panicle 

 sometimes contracted into a dense cylindrical spike or head. Stamens not 

 more than three. 



Here belong the fox-tail grasses, Alopecurus ; Timothy grass, or Herds' 

 grass of New England, Phleum pratense ; Rush grass, Vilfa ; Bent grass, 

 Agrostis : Red-top, or Herds' grass of Pennsylvania, A. vulgaris ; &-c. 



Tribe 10. PanicecB. Spikelets two-flowered ; inferior flower incomplete, 



G9 



