6 BULLETIN 772, U. S. DEPARTMENT OF AGRICULTURE. 



cjiryopsis (the single seed and the adherent pericarp) may be free, 

 as in wheat, or permanently inclosed in the lemma and palea. as in 

 the oat. Rarely the seed is free from the pericarp, as in species of 

 Sporobolus and Eleusine. The culms of bamboos are woody, as are 

 also those of a few genera, such as Olyra and Lasiacis, belonging to 

 other tribes. The culms are solid in our species of the tribes Trip- 

 saceae and Andropogoneae. The margins of the sheaths are grown 

 together in species of Bromus, Danthonia. Festuca, Melica, Panicu- 

 laria, 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 the palea is obsolete. 



Most of the genera of grasses fall naturally into one of the two 

 series or subfamilies. The remaining few are rather arbitrarily as- 

 signed to one or the .other series. In the same manner, most of the 

 genera may be assembled into distinct and w T ell-marked tribes, but 

 several are not closely allied to the other genera in the tribe to which 

 the} 7 are assigned but are so placed for convenience in classification. 



DESCRIPTIONS OF THE SUBFAMILIES AND KEYS TO THE TRIBES. 



SUBFAMILY 1, POATAE. 



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 Campulosus, TJniola, and Blepharidachne) ; articulation 

 usually above the glumes; spikelets usually more or less laterally 

 compressed. 



Key to the t riles of Poatae. 



riiints woody, the culms perennial; spikelets several-flowered. 



1. Bamboseae (p. 22). 

 Plants herbaceous, the culms annual. 



Spikelets with 2 staminate, neuter, or rudimentary lemmas unlike 

 and below the fertile lemma; no sterile or rudimentary rtoivts 



above 8. Phalarideae (p. 199). 



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 Blepharidachue). 

 Spikelets unisexual, articulate below the glumes, 1-flowered, 



terete or nearly so 10. Zizanieae (p. 200). 



Spikelets perfect (rarely unisexual but then not as above), usu- 

 ally 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. 204), 



