1] VEGETATIVE CHARACTERS 45 
Poa pratensis presents similar difficulties to P. trivialis: for 
diagnoses see p. 42. It is distinguished from P. nemoralis by its 
closed sheath, thicker, blunter and harder leaves, lnear-elliptical 
shoot-sections, and light coloured nodes, as well as by its habit. All 
other Poas have shallow and poorly developed roots. 
P. fertilis is a form very like P. nemoralis, with rougher leaves 
and longer ligule, introduced into cultivation. 
** Margins of leaves scaberulous with descending hairs. 
Very low flat ridges. Sheath smooth. 
Briza media, L. (Quaking Grass). A weed in meadows, 
indicating poor soil—e.g. moorlands and chalk—but eaten 
by sheep. Tufted and slightly creeping perennial. Ligules 
very short, entire. 
Briza minor, L. (Lesser Quaking-grass) Annual. 
Leaves broader and shorter, and ligules longer. In the 
south and rarer. 
a8 SHEATHS SPLIT, AT LEAST SOME DISTANCE DOWN. 
A. Glabrous—i.e. with no obvious hairs!. 
(a) Grasses with setaceous or bristle-like leaves ;— 
ie. the lamina of the lower leaves remains 
permanently folded instead of opening out flat. 
(1) Ligule obsolete, auricled at the junction of blade and 
sheath. 
Festuca ovina (Sheep’s Fescue). Densely tufted per- 
ennial. Leaves hard, glabrous and often glaucous, with 
5—7 ridges if forcibly unrolled, ears short, stiff and erect. 
Branches in permanent sheaths. Chiefly useful as pastures 
1 They may have short microscopic asperities, but there are no 
distinct long hairs. 
