,54 GRASSES OF SCOTI,AND. 



of the lloret, and not extending beyond the jagged summit. (Plate 

 XXIIL) 



Description. — It grows from twelve to eighteen inches high. The 

 root is perennial, fibrous. Stem erect, round, smooth, and pohshed ; 

 bearing three or four leaves with smooth striated sheaths ; the up- 

 per sheath longer than its leaf, crowned with a membranous acute 

 ligule. Joints smooth. Leaves narrow, acute, mostly involute,, 

 roughish on the inner surface and margins, smooth on the back, and 

 strongly ribbed. Inflorescence compound panicled. Panicle erect, 

 slightly drooping at the summit, of a silky brown appearance ; bran- 

 ches capillary, smooth, arranged on the smooth rachis in pairs, at 

 certain distances. Spikelets numerous, with very delicate footstalks ; 

 of two, sometimes three-awned florets, the lower floret not protruding 

 beyond the calyx. Cal7/z of two nearly equal acute membranous 

 smooth glumes, (Fig. 1 ) ; the upper glume three-ribed ; the lower 

 without lateral ribs, and smooth on the keel. Florets of two palese, 

 (Fig. 2); the outer palea of lowermost floret shorter than the glumes^ 

 of an oval form, jagged at the summit, hairy at the base, without la- 

 teral ribs ; keel roughish, furnished with a short rough aw7i aris- 

 ing from a little above the centre, and extending as high as the sum- 

 viit of the palea. Inner palea rather shorter than the outer palea, 

 membranous, and minutely fringed at the margins. Second floret 

 elevated on a hairy pedicle, rather smaller than the lower floret, but 

 similar to it in every other respect. 



Obs. — This grass is readily distinguished from Airajiexuosa, which 

 it somewhat resembles, in the awn arising from above the centre of the 

 palea, and not extending beyond the summit of the palea ; — whereas 

 in A.jiexuosa the axon arises from a little above the base, and extends 

 considerably beyond the summit of the palea. (See Plate XXIV. 

 Fig. 2.) 



From Aira ccBspitosa, in the awn arising from a little above the 

 centre of the outer palea ; — whereas in A. ccBspitosa the awn arises 

 from a little above the base of the outer palea. (See Fig. 2.) 



Aira alpina is not unfrequently met with on several of the High- 

 land mountains in Scotland, Ben Lomond, Ben Arthur, and moist 

 rocks in Angus-shire, but is not found in England or Ireland, or below 

 latitude 65. It is a northern plant, frequent in Lapland, and the 



