212 GRASSES OF BRITAIN. 



PoA ALPiNA (variety) vivipara. 



Viviparous Alpine'J^Ieadoio- Grass. 



Plate XCIV. 



This variety ^is frequent on most of the lofty mountains in Scot- 

 land, Ireland/and Wales,°growing on the ridges of wet rocks, usually 

 at an elevation of about 3600 feet above the level of the sea. The 

 principaVmark of ^distinction in this variety rests on* the transforma- 

 tion of the inner palea into leaves. 



The only plant it is likely to be mistaken for is Poa laxa^ figured 

 in Plate XXXVIII/; from which it differs in the whole plant be- 

 ing stouter. Root tufted. Glumes rounded at the base. Leaves 

 broader, shorter, more linear, folded and rounded at the summit, and 

 terminating in a minute mucro; — whereas in Poa laxa the whole 

 plant is more slender. Root not tufted. Glumes forming an ob- 

 tuse angle at the base. Leaves flat, lanceolate, and acute. 



Poa laxa was formerly considered to be a very rare British grass, 

 found only on Ben Nevis. Professor Balfour, however, has recently 

 discovered it growing plentifully on the rocks at Lochnagar, where 

 he gathered nearly a hundred specimens, both in the natural and 

 viviparous state. 



Explanation of Plate XCIV. Poa alpina (variety) vivipara, na- 

 tural size. 



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



2. Glumes. 



3. Florets in a viviparous state, the inner palea and upper florets trans- 



formed into leaves. 



4. Ligule of upper sheath. 



5. Upper leaf, showing the blunt ligule and rounded summit ; the back 



and margins minutely toothed. 



^1 



