160 CLASSIFICATION OF [CH. 



palea, bifid at its apex, tiirough which the yellow caryopsis 

 shines. 



Awn slender, basal, dark-brown, with oblique colourless 

 hairs above the middle and with a slight swelling above. 



The palea has a few hairs on its mid-rib below. 



Caryopsis about 1 mm. long. 



This grass is somewhat rare in England. The jointed basal awn, 

 with a minute hair-tuft above the middle, is unique, and readily 

 distinguishes it when mixed with Agrostis. 



© © Aion not bearded or thickened. 



= Palea bifid at apex. 



Air a caryophyllea. 

 A. prcecox. 



Air a caryophyllea, L. 



"Seed" 1-4 — 1'6 mm., comma-shaiDcd and dark-brown. 



Palea acute, nerveless, inrolled at edges and with a 

 dorsal, kneed, very fine, dark twisted awn twice as long as 

 the palea : the latter with two-toothed apex and a basal 

 hair-tuft. 



A common impurity in commercial seed. 



Aira prcecox^ L. is very similar, and cannot be distinguished 

 with certainty by the " seed," but has a shorter awn and no basal 

 hairs. Apex of palea two-toothed. 



= = Palea jagged or toothed, but not bifid. 



Aira flexuosa. 

 A. ccespitosa. 



Aira flexuosa, L. (Fig. 70). 



Palea 5 mm. long, four-toothed at the apex, and 

 caryopsis 2*6 mm. The fine basal awn waved or kneed, 

 about twice as long as the palea. Fruit with a groove. 



