6 
BULLETIN 772, U. S. DEPARTMENT OF AGRICULTURE. 
caryopsis (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the palea is obsolete.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 well-marked tribes, but 
several are not closely allied to the other genera in the tribe to which 
they 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, Uniola, and Blepharidachne) ; articulation 
usually above the glumes; spikelets usually more or less laterally 
compressed. 
Key to the tribes of Poatae. 
Plants 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 florets 
above S. 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 Blepharidachne). 
Spikelets unisexual, articulate below the glumes, 1-flowered, 
terete or nearly so 10. Zizanieae (p. 206). 
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). 
