42 CLASSIFICATION ACCORDING TO [CH. 



shorter. Moreover P. pratensis is a creeping stoloniferous grass, 

 less harsh, and with less pointed leaves. 



The distance to which the sheath is torn may be from J to J 

 down. Leaves tend to remain oonduplioate. Margins serrulate with 

 teeth extremely short and directed forwards. 



(ii) Shoots compressed hut 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. 



Kootstock 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 ccendea, 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 roimder at the ends. 



Poa pratensis, L. is larger and more stoloniferous, with both 

 extra- and intra- vaginal branches, cxilms 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. 



