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 
ewropaeus is conspicuous; and in the other, at higher elevations, 
Ulex Gallit 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 
(Ulez 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 Faerées; and this would appear to be very closely 
