MANUAL OF THE GRASSES OF THE UNITED STATES 17 



Spikelets 2- to many-flowered. 



Glumes as long as the lowest floret, usually as long as the spikelet 

 (sometimes shorter in Sphenopholis) ; lemmas awned from the 

 back (spikelets awnless in species of Trisetum, Koeleria, 

 Sphenopholis; and Schismus) 4. Aveneae (p. 21) 



Glumes shorter than the first floret (except in Dissanthelium with 

 long rachilla joints) ; lemmas awnless or awned from the tip 

 or from a bifid apex 2. Festuceae (p. 17) 



SUBFAMILY 2. PANICOIDEAE 



Spikelets with one perfect terminal floret (disregarding those of the 

 few monoecious genera and the staminate and neuter spikelets) and 

 a sterile or staminate floret below, usually represented by a sterile 

 lemma only, one glume sometimes (rarely both glumes) wanting; 

 articulation below the spikelets, either in the pedicel, in the rachis, or 

 at the base of a cluster of spikelets, the spikelets falling entire, singly, 

 in groups, or together with joints of the rachis; spikelets, or at least 

 the fruits, more or less dorsally compressed. 



Key to the tribes of Panicoideae 



Glumes membranaceous, the sterile lemma like the glumes in texture. 



Fertile lemma and palea thinner than the glumes. Sterile lemma awned from 



the notched summit 11. Melinideae (p. 26) 



Fertile lemma and palea indurate or at least firmer than the glumes. 



12. Paniceae (p. 26) 

 Glumes indurate; fertile lemma and palea hyaline or membranaceous, the sterile 

 lemma like the fertile one in texture. 

 Spikelets unisexual, the pistillate below, the staminate above, in the same 



inflorescence or in separate inflorescences 14. Tripsaceae (p. 29) 



Spikelets in pairs, one sessile and perfect, the other pedicellate and usually 

 staminate or neuter (the pedicellate one sometimes obsolete, rarely both 

 pedicellate). Lemmas hyaline 13. Axdropogoneae (p. 27) 



DESCRIPTIONS OF THE TRIBES AND KEYS TO THE GENERA 



TRIBE 1. BAMBUSEAE 



Culms woody, perennial, usually hollow; spikelets 2- to several- 

 flowered, in panicles or racemes, or in close heads or fascicles; often 1 

 or more sterile lemmas at base of spikelet; lemmas usually awnless; 

 blades usually articulated with the sheath, flat, rather broad. Only 

 one genus, Arundinaria, is native within our limits. Several species 

 of this and other genera are cultivated in the Southern States. 



TRIBE 2. FESTUCEAE 



Spikelets more than 1-flowered, usually several-flowered, in open, 

 narrow, or sometimes spikelike panicles (rarely in racemes) ; lemmas 

 awnless or awned from the tip, rarely from between the teeth of a 

 bifid apex; rachilla usually disarticulating above the glumes and 

 between the florets. 



A large and important tribe, mainly inhabitants of the cooler 

 regions. The lemma is divided into several awns in Pappophorum and 

 its allies, is deeply 2-lobed in Triplasis and in a few species of Triodia, 

 3-lobed in Blepharidachne, several-toothed in Orcuttia, and slightly 

 2-toothed in Bromus and in a few other genera, the awn, when single, 

 arising from between the teeth. The paleas are persistent upon the 

 continuous rachilla in most species of Eragrostis. Scleropogon, 



