16 MISC. PUBLICATION 200, U. S. DEFT. OF AGRICULTURE 



few genera, such as Olyra and Lasiacis, belonging to other tribes. 

 The culms are solid in our species of the tribes Tripsaceae and Andro- 

 pogoneae and in several other groups. The margins of the sheaths 

 are grown together in species of Bromus, Danthonia, Festuca, Melica, 

 Glyceria,, and other genera. 



The parts of the spikelet may be modified in various ways. The 

 first glume, and more rarely also the second, may be wanting. The 

 lemmas may contain no flower, or even no palea, or may be reduced 

 or rudimentary. Rarely, as in species of Agrostis and Andropogon, 

 the palea is obsolete. 



The division of the family into two subfamilies is somewhat arti- 

 ficial. The tribes Zoysieae, Oryzeae, Zizanieae, and especially Phala- 

 rideae, do not fall definitely into either of the recognized subfamilies. 

 They are placed as indicated largely for convenience. 



DESCRIPTIONS OF THE SUBFAMILIES AND KEYS TO THE 



TRIBES 



SUBFAMILY 1. FESTUCOIDEAE 



Spikelets 1- to many-flowered, the reduced florets, if any, above 

 the perfect florets (except in Phalarideae; sterile lemmas below as 

 well as above in Ctenium, Uniola, and Blepharidachne) ; articulation 

 usually above the glumes; spikelets usually more or less laterally 

 compressed. 



Key to the tribes of Festucoideae 



Plants woody, the culms perennial. Spikelets several-flowered. 



1. BAMBUSEAE (p. 17) 



Plants herbaceous, the culms annual (somewhat woody and persistent in Arundo) . 

 Spikelets with 2 (rarely 1) staminate, neuter, or rudimentary lemmas unlike and 

 below the fertile lemma; no sterile or rudimentary floret above. 



8. PHALARIDEAE (p. 25) 



Spikelets without sterile lemmas below the perfect floret (or these rarely present 

 and like the fertile ones, a dissimilar pair below and a rudimentary floret 

 above in Blepharidachne). 

 Spikelets unisexual, falling entire, 1-flowered, terete or nearly so. 



10. ZIZANIEAE (p. 26) 

 Spikelets perfect (rarely unisexual but then not as above) , usually articulate 



above the glumes. 



Spikelets articulate below the glumes, 1-flowered, very flat, the lemma and 

 palea about equal, both keeled. Glumes small or wanting. 



9. ORYZEAE (p. 25) 

 Spikelets articulate above the glumes (rarely below, but the glumes, at 



least one, well developed). 



Spikelets 1-flowered (or the staminate 2-flowered) in groups (short 

 spikes) of 2 to 5 (single in Zoysia), the groups racemose along a 

 main axis, falling entire; lemma and palea thinner than the glumes. 



6. ZOYSIEAE (p. 24) 

 Spikelets not as above. 



Spikelets sessile on a usually continuous rachis (short-pedicellate in 

 Leptochloa and Trichoneura; the rachis disarticulating in Lep- 

 turns, Pholiurus, Hordeum, Sitanion, and in a few species of 

 allied genera). 

 Spikelets on opposite sides of the rachis; spike terminal, solitary. 



3. HORDEAE (p. 20) 

 Spikelets on one side of the rachis; spikes usually more than 1, 



digitate or racemose 7. CHLORIDEAE (p. 24) 



Spikelets pedicellate in open or contracted, sometimes spikelike, 



panicles, rarely racemes. 



Spikelets 1-flowered (occasionally some of the spikelets 2-flowered in 

 Muhlenbergia asperifolia and M. arenacea). 



5. AGROSTIDEAE (p. 22) 



