GRAMINEAE 37 



52. AGROPYRON Gaertn. Couch Grass. 

 Spikelets 3-niany-flowerecl, sessile and alternate at each joint of the 

 continuous rachis. Two lower glumes empty, the flowering 5-7-nerved, 

 rounded on the back and usually short-awned. 



Plants with running rootstocks. 



Plants glaucous ; spikelets divergent. 1. A. occidentale. 



Plants green ; spikelets appressed. 



Empty scales much shorter than the flowering. 2. A.repens. 

 Empty scales almost equal to the flowering. 3. A. pseudorepens. 



Plants without running rootstocks. 



Awns shorter than flowering glumes. 4. A. ienerum. 



Awns as long as flowering glumes. 5. A. caninmn. 



1. A. occidentale Scribn. & Smith. 2°-3° high : leaves involute 

 ■when dry, smoothish beneath, scabrous above : spike V-1^ long : spike- 

 lets Q^^-9^^ long, 6-10-flowered : glumes acuminate or short-awned. — 

 Commonly introduced along railroads, where it occurs in great beds. 

 June-July. 



2. A. repens ( L. ) Beauv. 2°-4° high : leaves flat, 7'-10^ long, 

 rough above, smooth beneath : spike 5'-ll^ long: rachis slightly hispid 

 to pubescent : spikelets 6^^ long, 3-7-flowered : the glabrous glumes 

 short-awned. — Adventized along railroads, especially at Lee's Summit 

 where a peculiar pubescent forms occurs. June-July. 



3. A. pseudorepens Scribn. & Sn)ith. Eesembles the last, but the 

 leaves are rough on both sides and the empty glumes nearly equal the 

 flowering ones. — Sparingly adventized at Courtney and Sheffield. July- 

 August. 



4. A. tenerum Vasey. l2°-2j° high: leaves narrow and rough: 

 spike slender, 3^-6^ long, the few-flowered spikelets appressed to the 

 rachis, 4^^-7^' long : empty glumes S-nerved, acute, the flowering acu- 

 minate or short-awned. — Rarely adventized at Sheffield. June-July. 



5. A. caninum (L. ) R. & S. l°-3° high : lower sheaths often pubes- 

 cent : leaves rough above, smooth beneath : spikes densely flowered, 4^-1^ 

 long, the spikelets 6'^ or more long. — Rarely adventized along railroads. 

 June-July. 



53. HORDEUM L. 

 Flowers in close terminal spikes three at each joint of the rachis, but 

 the lateral flowers imperfect and stalked. Central flower sessile, its flow- 

 ering glume long awned. Empty glumes 6, awn-pointed, forming a sort 

 of an involucre. 



Awn of flowering glume 6^^ or less long. 1. R. pusillum. 



Awn of flowering glume S''^ or more long. 2. H. jubatum. 



1. H. pusillum Nutt. Wild Barley. Erect annual, G'-IS^ high : 

 spikes 1^-3^ long, 3^^-4'^ wide : four middle empty glumes dilated above 

 the base, the two lateral awn-like : lateral flowers not awn-pointed. — 

 Common in dry soil throughout. May-June. 



