340 GRASS FAMILY 



m. Spikelets in 3's in a cylindric spike 

 with zig-zag axis; lemma and 

 palet like the glumes in texture HILARIA 

 n. Spikelets in panicles, or in spikes, 

 not in 3's; lemma thicker and 

 harder than the glumes 

 (m) Spikelets in a spiny bur-like 



involucre CENCHRUS 



(n) Spikelets not in a bur 

 r. Spikelets in one-sided racemes 



or spikes 



(r) Spikes 1-2 PASPALUM 



(s) Spikes 3-10 DIGITARIA 



s. Spikelets in a panicle or cylin- 

 dric spike 



(r) Spikelets in a panicle 

 h. Spikelets solitary, not 



awned PANICUM 



i. Spikelets in spike-like 



groups, awned ECHINOCHLOA 



(s) Spikelets in a cylindric 

 spike with an involucre 

 of bristles CHAETOCHLOA 



AGROPYRUM Gaertner 1770 WHEAT GRASS, QUACK GRASS 



(Gr. agros, field, pyron^ wheat, from the habitat of the quack grass) 



PL 46, fig. 26, 27. 



Spikelets 3-many-flowered, in a terminal spike, sessile, and single at 

 each joint of a more or less zig-zag axis, the face of the spikelet turned 

 toward the axis ; glumes 2, lanceolate or lance-linear, often awned ; lemma 

 rounded on the back, 5-7-nerved, acute or awned, palet 2-keeled, the keels 

 often ciliate; annual or perennial. 



1. Stems in bunches, without creeping rootstocks or 

 stolons 



a. Awns 2-3 cm. long; stems spreading or pros- 



trate; at 10-13000 ft. A. Scribneri 



b. Awns less than 2 cm. long; stems erect; at 4- 



10000 ft. 



