TO THE GENERA OF THE FAMILY GRAMINE&. 10$ I 



v Empty glumes minute; low arctic grasses with dense in- 

 florescence PHIPPSTA. 



w Empty glumes one-half length of fl. glumes or more. 

 w Spikelets very densely spicate; upper sheaths inflated. 



HELEOCHLOA. 



ww Spikelets interruptedly spicate or open-paniculate. 

 ot Third glume shorter than the 2d, rarely equaling it, 



hyaline AGROSTIS. 



XX Third glume equaling 2d or longer, membranous, not 



hyaline. 

 . y Arctic grasses; 3d glume obtuse, hispid on keel. 



ARCT AGROSTIS. 

 yy Not arctic; 3d glume acute or obtuse, not distinctly 



hispid on keel. 

 z Rootstock densely scaly; 3d gl. usually 3-nerved; 



grain inclosed by glume MUHLENBERGIA. 



22 No densely scaly rootstocks; 3d glume usually 



i -nerved; grain and seed free SPOROBOLIS. 



qqq Glumes four or more, only the ist and zd occasionally very 



dissimilar from other in size. 

 r Glumes 4, but the 3d glume empty or containing stamens only, 



membranous; the 4th coriaceous; e.g. = spk. 

 S Second glume much enlarged, saccate at base; panicle con- 

 tracted SACCIOLEPIS. 



ss Second glume not enlarged' nor saccate. 

 / Empty glume densely covered with long silky hairs which 



equal or exceed the spikelet (TRICHOL,ENA ; ) 



tt Empty glume not long-silky PANICUM. 



rr Glumes 4 or more, all similar in texture, or the lower two 



firmer. 



S Very large grasses 2-6 m. high, with the very long rigid re- 

 curved leaves densely clustered at base; not hardy north; 



e.g. < spk (GYNERIUM.) 



SS Smaller grasses not as above (Uniola 25 dm. tall, but leaves 



ordinary). 



t Spikelets truly spicate, turned with their edges toward the 

 axis and the empty glume in the axil regularly absent; 



e.g. = or < spk LOLIUM. 



tt Spikelets paniculate, or if spicate then the side turned toward 



the axis and both empty glumes present. 

 Fl. glumes i-3-nerved. 



V First empty glume linear, acute, second broad oblanceolate 

 or obovate, truncate or abruptly acute; e.g. < spk. 



EATONIA. 



W Empty glumes not very dissimilar except in size. 

 w Lateral nerves of fl. glumes pilose; e.g.<spk. TRICUSPIS. 

 ww Lateral nerves glabrous. 



x Spikelets alternate and distant, in a true spike, lanceo- 

 late acute; fl. glume i -nerved; e.g. = spk. 



LEPTURUS. 



xx Spikelets paniculate; e.g.<spk. 

 y Flowering glumes keeled. 

 2 Inflorescence contracted; spikelets very flat, 2-c;-fld. 



KOELERIA. 



22 Inflorescence open; spikelets 2-;?5-fld.ERAGROSTis. 

 yy Flowering glumes rounded on the back. 

 2 Panicle narrow, more or less contracted. 

 2 1 Fl. glume coriaceous when mature; seed beaked. 



KORYCARPUS. 



