IV] GRASSLAND ASSOCIATIONS 109 



and it is probable that the present upper altitudinal limits of 

 the bracken approximate very closely with the upper altitudinal 

 limits of the ancient and pre-historical forests. Sometimes the 

 bracken spreads from the Nardus grassland into the adjoining 

 moorland associations, not uncommonly into the heather 

 (Calluna vulgaris) moor when this occurs in rather sheltered 

 valleys and depressions, and rarely into the cotton-grass 

 (Eriophorum vaginatum) moor when the peat of this is be- 

 coming drier. In the Peak District, the bracken commonly 

 ascends to 1500 feet (457 m.) or 1550 feet (472 m.), above which 

 altitudes it becomes local and rare. Woodhead (1906 : 360) 

 states that it ascends to 1700 feet (518 m.); but in England 

 it is quite exceptional to meet with the plant at such an 

 altitude. 



Pethybridge and Praeger (1905 : 155) describe areas of 

 bracken in the district south of Dublin. The list of species 

 which these authors give indicates that species characteristic of 

 Nardus grassland are numerous in such areas. The authors 

 state that in the month of May, the bracken areas often exhibit 

 glorious sheets of blue, white, and yellow due to the abundance 

 of the blue-bell (Scilla non-scripta), violet (Viola Riviniana), 

 speedwell (Veronica Chamaedrys), earth-nut (Conopodium 

 majus), lesser celandine (Ranunculus Ficaria), and primrose 

 (Primula vulgaris). Such a display of flowers is unknown in 

 connection with the bracken areas of the upland slopes of 

 the Pennines, but may occasionally be seen as the lowlands are 

 reached. 



Pethybridge and Praeger (1905: 150 and 153) map two 

 plant communities of gorse. In one, at lower altitudes, Ulex 

 europaevs is conspicuous ; and in the other, at higher elevations, 

 Ulex Oallii is exceedingly abundant. In this district, the two 

 species have similar altitudinal relationships ; but they are not 

 specially abundant, especially U. europaeus. In Somerset, 

 this altitudinal relationship perhaps does not hold good, ' for 

 the two species frequently occur side by side. In certain 

 localities in the south of England, a third species of gorse 

 ( Ulex minor = U. nanus) becomes locally a very important 

 element on heaths and heathy grasslands. 



Ostenfeld (1908: 966) has described a grass-slope "forma- 

 tion " of the Faeroes ; and this would appear to be very closely 



