44 



to elevate and solidify low lands liable to be overflowed by rivers ; 

 and, where they occur on hill and mountain slopes, by binding 

 the spongy soil and preventing the slips which would leave them 

 bare. 



AiRA ALPiNA. Smooth Alpine Hair Grass. Plate XXXVII. 



Panicle rather contracted ; its branches smooth. Glumes smooth 

 on the midvein. Flowers hairy at the base; two, with the rudi- 

 ment of a third. Awn bent, twisted at the base, arising from 

 above the middle of the lower palea and scarcely exceeding it in 

 length. Leaves involute. 



Aira alpina, Linrums. E.B. ed. 3. 105. Generally adopted. 

 A. Isevigata, E. B. 2102. 



Found growing in the moist crevices of rocks about the summits 

 of the Highland and Welsh mountains. lu these habitats it has 

 rarely the tufted character of the preceding species, but often 

 exhibits a tendency to creep and send out stolones. The stems 

 are seldom more than a foot high, and occasionally only three or 

 four inches. The leaves are short, turned inwards on the margins, 

 which gives them a narrow appearance, rigid, and roughish on the 

 upper surface. The panicle varies much in size and compactness, 

 being in some instances more expanded than represented in our 

 figure, in others having the branches almost close. The spikelets 

 are much larger than those of the normal form of A. ccespitosa ; 

 they are far more frequently viviparous than fruit- bearing. The 

 awn, though usually arising from above the middle of the back of 

 the lower palea, has sometimes a lower attachment ; neither is its 

 bent and twisted character always appreciable. 



Perennial. Flowers in July. 



This differs sufficiently from the last in general aspect to admit 

 the probability of its being a distinct species, were the above- 

 mentioned varieties wanting, but their occurrence renders the 

 question doubtful. Having only grown the viviparous form of 

 A. alpina, I have no evidence to adduce concerning its suspected 

 identity with the alpine conditions of A. ccespitosa, but believe in 

 it notwithstanding. . 



AiRA FLEXuosA. Wavcd Hair Grass. Plate XXXVIII. 



Panicle spreading; its branches waved. Glumes roughish on 

 the midvein. Flowers hairy at the base ; two, with the rudiment 

 of a third. Awn jointed, arising from near the base of the lower 

 palea, and extending considerably beyond its apex. Leavesalmost 

 setaceous. Ligule truncate. 



