TO THE GENERA OF THE FAMILY GRAMINEJE. I05I 



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

 florescence Phippsia. 



vv 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. 

 x 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. 



Arctagrostis. 

 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 Mtjhlenbergia. 



zz No densely scaly rootstocks; 3d glume usually 



1 -nerved; grain and seed free Sporobolis. 



qqq Glumes four or more, only the 1st and 2d 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. 



, W Second glume not enlarged nor saccate. 



t Empty glume densely covered with long silky hairs which 



equal or exceed the spikelet (Trichol^:n t a.) 



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 (Gynertum.) 



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



ordinary). 

 / 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. 

 u Fl. glumes 1-3-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-^-fld. 



Koeleria. 

 zz Inflorescence open; spikelets 2-35-fld.ER agrostis. 

 yy Flowering glumes rounded on the back, 

 z Panicle narrow, more or less contracted. 

 z l Fl. glume coriaceous when mature; seed beaked. 



KORYCARPUS. 



