242 GRASSES OF BRITAIN. 



AiRA ALPiNA (variety) vivipara. 

 Viviparous Alpine Hair- Grass. 

 Plate CIX. 



This grass seems to be the Aira Icevigata figured in the English Bo- 

 tany, t. 2102, which, according to Sir William Hooker and other bo- 

 tanists, is the Aira alpina in a viviparous state. It is frequently met 

 with on several of the Scottish mountains, growing among moist or wet 

 rocks, usually at an altitude of between three and four thousand feet 

 above the level of the sea. It is said also to grow on some of the 

 higher mountains in Wales. The root is perennial, fibrous, tufted, 

 bearing a short, stout, perfectly-smooth stem. Sheaths smooth. 

 Licjule prominent and acute. Leaves acute, harsh, flat, (those of the 

 root mostly folded), rough and strongly ribbed on the inner surface, 

 smooth behind. Rachis and branches perfectly smooth. Spikelet 

 composed of two glumes and two florets, the florets being transformed 

 into small linear leaves curved at the summit, or frequently terminat- 

 ing in a small rough point or awn. Glumes w^axly equal, membran- 

 ous, tinged with purple, while the leafy florets are of a light green. 

 None of the viviparous grasses produce seed ; they propagate their 

 species through the medium of their florets, which fall and take root. 



The most prominent marks of distinction in this grass, independent 

 of its viviparous form, rest in the stem, sheaths, back of the leaves, 

 rachis, and branches being perfectly smooth. 



The accompanying figure was drawn from a specimen gathered on 

 Ben Lawers. 



Explanation of Plate CIX. Aira alpina (variety) vivipara, natu- 

 ral size. 



Fig. 1. Spikelet, showing the glumes and florets. 



2. Glumes, 



3. Florets transformed into small leaves. 



