I^IS] The Grasses op Illinois 271 



mm. Awn, if present, persistent; 

 lemmas lanceolate, 

 n. Glumes minute or ob- 

 solete ; rachilla pro- 

 longed beyond the 

 base of the palea; 

 floret stipitate. 



22. Brachyelytrum 

 nn. Glumes usually at least 

 half as long as the 

 spikelet (minute in 

 M. schreberi) ; ra- 

 chilla not prolonged; 

 floret not stipitate. 

 21. Muhleniergia 

 ii. Lemmas not indurate, at least not firmer than 

 the glumes, or if somewhat firmer, strongly 

 compressed and keeled, 

 j. Panicle compact, cylindrical; spikelets 

 strongly flattened and keeled, 

 k. Spikelets about 1 cm. long; floret 

 conspicuously hairy at base ; robust 

 perennial with stout, scaly root- 

 stocks. 30. Ammophila 

 kk. Spikelets not over 4 mm. long; lem- 

 ma not hairy at base; plants with- 

 out rootstocks. 

 1. Panicle partly included in a 

 broad subtending sheath; 

 glumes shorter than the lem- 

 ma. 23. Heleochloa 

 • 1!. Panicle not included in a sub- 

 tending sheath; glumes not 

 shorter than the lemma. . 

 m. Glumes abruptly aristate, 

 stiffly ciliate on the keel ; 

 lemmas awnless (timo- 

 thy). 24. Phleum 

 mm. Glumes not pointed nor cil- 

 iate on the keel; lemma 



,_ with a slender awn from 



the back. 25. Alopecurus 



j.j. Panicle open or contracted; spikelets 



not strongly flattened. 



k. Floret conspicuously hairy at base. 



1. Lemma with a delicate dorsal 



awn ; rachilla prolonged be- 



_ yond the base of the palea. 



29. Calamagrostis 

 11. Lemma awnless; rachilla not 

 prolonged. 28. Calamovilfa 

 kk. Floret not hairy at base. 



I. Lemma shorter than the glumes; 



palea usually wanting. 



27. Agrostis 



II. Lemma longer than the glumes 



or as long; palea present, 

 m. Florets stipitate; lemma 

 with a minute awn; pan- 

 icle drooping. 31. Cinna 



