Ill] VEGETATIVE CHARACTERS 47 



A. prcBcox, L. (Early Hair-grass). Greener and more 

 glabrous. Habit more rigid. 



A. canescens, L. (Grey Hair-grass). Glaucous or 



purplish; rare, on S.E. coasts. 



(y) Leaves narrow and more or less involute, and 

 subulate upwards, but easily unrolled, and apt to 

 become flatter as they age. 



Avena pratensis, L. (Perennial Oat). Leaves rather 

 thin, dry, harsh, ridgeless, with flanking lines and a keeV ; 

 glaucous, glabrous, but edges scabrous. Usually involute, 

 but may open out. Ligule long ovate-acute. Dry pastures, 

 especially on calcareous soil, and of little value. 



Poa inaritima, Huds. (Sea-grass). Leaves narrow, 



rather short, and U-shaped in section. Involute : ridgeless, 



with flanking lines, but no keel ; soft and rather thick. 



Ligule rather long, obtuse and decurrent. Useless 



agriculturally. 



For difficulties with other species of Avena and Poa see pp. 44, 

 54 and 60. 



(1)) Grasses with the leaves expanded, more or less 



flat. 



(1) Blades conspicuously ridged — i.e. the surface is raised 



in prominent longitudinal ridges with furrows between. 



(i) Leaves i-igid and hard, sharp pointed. Sheath and 



outer leaf-surface usually glabrous. 



Aira cwspitosa, L. (Tufted Hair-grass). Forms large 

 tufts. A coarse weed forming bad tussocks in wet meadows 

 and pastures: useless for fodder. Leaves flat. Ligule 

 long, acute. Ridges equal, high and sharp, and scabrid, 



1 Very like a Poa when opened out, but the leaves are scabrid at the 

 sheaths. 



