150 CLASSIFICATION OF [CH. 
No keel. Apex of inner palea bifid, outer mucronate. 
Fruit shelled. 
Easily distinguished from Digraphis arundinacea, which has 
a basal hair-tuft and very different caryopsis; less easily from 
Agropyrum and Lolium, except in the velvety surface. 
Fig. 63. Elymus aren- Fig. 64. Dactylis glomerata. a, spikelet 
aris: a, ** seed,” with glumes removed, nat. size; b, 
nat. size; b and ec, ditto, x about 6; ¢ and d, “seed,” nat. 
the same, x3. Note size (below) and xabout 6. The stiff 
the stiff, velvety, bifid and slightly curved awn-point is sub- 
and mucronate outer terminal and arises from between two 
palea, and the large teeth. Rachilla dilated above. Nobbe. 
hairy rachilla. Nobbe. Cf. Fig. 60. 
Agropyrum repens may have a mucronate awn-point 
or not. The small palea 10—12, the caryopsis 5—6 mm. 
(see p. 169 for description). 
This troublesome weed (Couch-grass) presents similar difficulties 
with Lolium perenne that Agropyrum caninum does with Lolium 
temulentum—see p. 168. It is moreover extremely variable. 
