ut] VEGETATIVE CHARACTERS 47 
A. precox, 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 keel’; 
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 maritima, 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. 
(b) 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 rigid and hard, sharp pointed. Sheath and 
outer leaf-surface usually glabrous. 
Aira cespitosa, 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. 
