324 American Midland Naturalist Monograph No. 7 



5. Lemmas longer than the gkimes, awnless or with a straight 



apical awn Tribe 2. Festuceae 



5. Lemmas usually shorter than the glumes. 



6. Florets essentially uniform, the lemmas usually with a bent 

 awn arising from the back Tribe 4. Aveneae 



6. The two lower florets sterile or staminate, unlike the single 



fertile floret; spikelets awned or not Tribe 7. Phalarideae 



4. Inflorescence of soHtar>', racemose, or digitate spikes or racemes, 

 the spikelets sessile or nearly so. 

 7. Spikelets solitary, or in clusters of 2-6, arranged alternately on 



opposite sides of the axis; spike solitary, terminal 



Tribe 3. Hordeae 



7. Spikelets in one-sided spikes or racemes, the spikes or racemes 



solitary or several Tribe 6. Chlorideae 



3. Spikelets 1 -flowered. 



8. Glumes 2; stamens 3 or 1 Tribe 5. Agrostideae 



8. Glumes none; stamens 6 Tribe 8. Oryzeae 



1. Spikelets more or less dorsally compressed with only one perfect terminal 

 floret whose lemmas resemble glumes; articulation below the spikelets, 

 these falling entire. (Subfamily IL Panicoideae) 

 9. Stamens and pistils in the same inflorescence, usually in the same spike- 

 let or floret. 



10. Spikelets essentially vmiform Tribe 9. Paniceae 



10. Spikelets in pairs or threes, one sessile and fertile, the others pedi- 

 celled and staminate or neuter, or rarely absent or reduced to a 



pedicel Tribe 10. Andropogoneae 



9. Staminate and pistillate spikelets in diflPerent parts of the same spike, or 



in different inflorescences, the staminate above the pistillate ones 



Tribe 1 1. Tripsaceae 



Key to the Genera 



Subfamily 1. Poacoideae 



Tribe 1. Bambuseae. — Bamboo Tribe 



One genus in Illinois 1. Arundinaria 



Tribe 2. Festuceae. — Fescue Tribe 



1. Plants 2-4 m tall; rachilla plumose; panicles large 14. Phragmites 



1. Plants less tall; rachilla not plumose. 



2. Plants dioecious, the staminate and pistillate flowers unlike ....18. Distichlis 

 2. Plants with perfect flowers in uniform spikelets. 

 3. Lemmas prominently 3-nerved. 



4. Lemmas more or less villous on the ner\es. 



5. Stem-nodes glabrous; palet not ciliate 16. Tridens 



5. Stem-nodes pubescent; palet conspicuously ciliate 17. Triplasis 



4. Lemmas glabrous, or merely scabrous on the nerves. 



6. Callus of lemma heavily bearded 13. Redfieldia 



6. Callus of lemma not bearded. 



7. Lemmas less than 5 mm long 9. Eragrostis 



7. Lemmas about 8 mm long; the upper 2-4 lemmas empty 



10. Diarrhena 



3. Lemmas 5- to many-nerved (the nerves sometimes indistinct). 

 8. Spikelets with sterile lemmas above or below the fertile florets. 



