178 FLOWERS OF ROCKS, WALLS, ETC. 



The Butterfly, The Grayling (Satyrus semele), and two moths, The 

 Slender Clouded Brindle (Xylopkasia scolopasina), Elachista elcochar- 

 ella, are found on it. 



Aira, Theophrastus, from Greek airo, I destroy, was the name of 

 a grass probably Darnel which was poisonous. The second Latin 

 name is given in allusion to the scent of cloves, which makes it attrac- 

 tive to Lepidoptera. It is called Mouse-grass. 



ESSENTIAL SPECIFIC CHARACTERS: 



333. Aira caryophyllea, L. Stem erect, leaves setaceous, short, 

 narrow, sheaths rough below, panicle spreading, awn silvery, twisted. 



Flat-stalked Poa (Poa compressa, L.) 



This more or less local mural grass is found in the N. Temperate 

 Zone in Europe, N. and W. Asia, and is possibly native in America, 

 there being no trace of it in early plant beds. In Great Britain it does 

 not grow in the Peninsular province in W. Cornwall, but throughout 

 the Channel and Thames, Anglia, and Severn provinces, except in 

 Stafford; in S. Wales, only in Carmarthen and Pembroke; in N. 

 Wales, in Denbigh, Anglesea; in the Trent province; in the Mersey, 

 not in Chester; throughout the Humber, Tyne, and Lakes pro- 

 vinces, except in the Isle of Man; and in the W. Lowlands, only 

 in Renfrew and Lanark; in the E. Lowlands, only in Roxburgh, Ber- 

 wick, Edinburgh; in the E. Highlands, in Fife and Forfar; in N. 

 Highlands, in E. Ross. From Ross it ranges southward, but it is rare 

 in Ireland and the Channel Islands. 



The Flat-stalked Poa is not so common as some others, on account 

 of its restricted habitat. It prefers a dry soil, and largely affects a 

 mural habitat. Thus it grows commonly on walls with Vernal Grass, 

 Mouse-ear Hawkweed, &c., and its mitural habitat is a dry bank. 



Slightly prostrate at the base, the stem is finally erect, oblique, 

 flattened (hence the second Latin name), from a creeping rhizome 

 which produces long soboles. The leaves are flat, rough or smooth. 

 The upper leaf is longer than the sheath, with the upper knot near the 

 middle of the stem. The ligule is short and blunt. 



The flowers are in a secund (one-sided) branched panicle, which is 

 narrowed. The spikelets have 5-7 flowers, and are oblong, egg-shaped, 

 bluish-purple, with hyaline flowering glumes, with 3 hairy veins, and 

 webbed, blunt, and smooth. 



Flat-stalked Poa is 1-2 ft. high. The flowers are in bloom in 

 June and July. The plant is perennial, propagated by division. 



