42 CLASSIFICATION ACCORDING TO [CH. 
shorter. Moreover 2. pratensis is a creeping stoloniferous grass, 
less harsh, and with less pointed leaves. 
The distance to which the sheath is torn may be from } to 4 
down. Leaves tend to remain conduplicate. Margins serrulate with 
teeth extremely short and directed forwards. 
(11) Shoots compressed but narrow: the section almost 
rhomboid with rounded edges. 
Poa trivialis, L. (Rough-stalked Meadow-grass). Con- 
spicuous in deep rich pastures and orchards, preferring 
slight shade and rich soil. Valuable pasture and hay 
grass. 
Rootstock shortly creeping, branches extra-vaginal and 
above ground, shoots rough. Blade narrow, harsh, with an 
acute point, thin, shining below, ridgeless, with flanking 
lines and keel. Ligule acute, and short or long (Fig. 8). 
Sesleria coerulea, Ard. (Blue Moor-grass), of our 
northern limestone hills, has narrow, flat, glaucous blue, 
stiff, mucronate leaves, with scabrid apex. Ligule ciliate. 
Poa trivialis is most likely to be confounded with other Poas, 
especially P. annua and P. pratensis, since they both have thin 
leaves and flat shoots ; but P. annua has a split sheath, less acute 
and duller leaves, is annual, and less harsh, and the shoot-section is 
flatter at the sides and rounder at the ends. 
Poa pratensis, L. is larger and more stoloniferous, with both 
extra- and intra-vaginal branches, culms erect and smooth, sheaths 
smooth, and the shoot-sections elliptical—not cornered or rhom- 
boidal—and with darker green and larger, thicker, 7-veined, more 
glossy, and less harsh leaves, with shorter, blunter ligule. 
Poa compressa, L. also presents difficulties, but the sheath is 
split, and the ligule is shorter than in P. trivialis, the leaves thicker, 
and the shoot-sections more linear-oblong or elliptical. 
(8) Sections of sheathed leaves rounded, circular or 
oval, there being no prominent keels. 
