MANUAL OF THE GRASSES OF THE UNITED STATES 15 



and Trichoneura; the rachis disarticulating in Monerma, Parapholis, Hor- 

 deum, Sitanion, and in a few species of allied genera. See also Brachypo- 

 dium in Festuceae.) 

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



3. Horde ae (p. 230) 

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



racemose 7. Chlorideae (p. 491) 



Spikelets pedicellate in open or contracted, sometimes spikelike, panicles, rarely 

 racemes. 

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



species of Muhlenberqia) 5. Agrostideae (p. 313) 



Spikelets 2- to many-flowered. 



Glumes as long as the lowest floret, usually as long as the spikelet (some- 

 times shorter in Sphenopholis) ; lemmas awned from the back (spikelets 

 awnless in species of Trisetum, Koeleria, Sphenopholis, and Schismus). 



4. Aveneae (p. 280) 

 Glumes shorter than the first floret (except in Dissanthelium with long 



rachilla joints, and in Tridens strictus) ; lemmas awnless or awned from 

 the tip or from a bifid apex 2. Festuceae (p. 31) 



SUBFAMILY 2. PANICOIDEAE 



Spikelets with 1 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, 1 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. 569) 



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



12. Paniceae (p. 569) 

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

 the fertile one in texture. 

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



or in separate inflorescences 14. Tripsaceae (p. 789) 



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. Andropogoneae (p. 737) 



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 Tridens , 3-lobed in Blepharidachne, 



