ch. vn] Botanical Description of Species 129 



completely removed. In bulk the "seed" almost always has a 

 darker brown appearance than that of P. trivialis. 



Poa rigida, L. An annual, frequently found in rocky situa- 

 tions, on old walls, etc. Flowers in July, the culms seldom more 

 than 6 inches high. Panicle secund. Spikelets about seven- 

 flowered. Glumes without lateral nerves. Palese not "webbed" 

 at the base. (Figs. 144 and 145.) 



Poa trivialis, L. (Eough-stalked Meadow-grass.) (Fig. 141.) 

 See p. 161. 



A perennial, abundant in moist pastures etc. throughout the 

 British Isles. Whilst young it forms tufts (and remains tufted if 

 grown under dry conditions), but later, and especially in the 

 presence of moisture, it covers large patches of ground by forming 

 roots and tufts of foliage at the nodes of its numerous thin stolons. 

 Young shoots compressed. Sheaths entire, sharply keeled, those 

 of the young foliage smooth, but those of the flowering culms 

 rough (upwards). Blade conduplicate, broadest near base, and 

 tapering gradually to a sub-acute point. Upper surface dull, 

 ribless. Lower surface keeled and glossy. Ligule of the upper- 

 most leaf long and glossy. No auricles. 



Flowers about midsummer; the culms erect, from 1 to 2 feet 

 or more in height. Panicle erect, with rough spreading branches. 

 Spikelets ovate, 2-5 flowered, but usually with two or three 

 flowers. Upper empty glume slightly larger than the other glume 

 and three-nerved. Both glumes have scarious margins and are 

 sharply keeled; the keels are distinctly toothed. 



"Seeds" 1-8 to 2-5 mm. long, and narrower than those of 

 P. pratensis. Outer palea acute at the apex, five-nerved; only 

 the dorsal and marginal nerves are prominent, which gives a 

 sharply triangular cross-section to the "seed." Hairs may be 

 present on the lower half of the dorsal nerve (keel), but none are 

 present on the remaining nerves. The "web" at the base of 

 the palese is less copious than that of P. pratensis. Commercially 

 cleaned "seeds" are usually quite free from hairs except for a 

 trace of the "web." (Fig. .143.) 



Psamma arenaria, Beauv. (Sea Mat-grass.) (Fig. 146.) 



A perennial, frequerit on our sea coasts. It has extensively 

 creeping rhizomes and is therefore useful as a sand-binder. Leaf- 



a. 9 



