PLANTING OF WATER CATCHMENT AREAS 111 
becomes deeper and wetter, especially on the badly drained 
plateaux, and heather ceases to grow or loses its vigour, 
becoming thin and stunted. On the wet moors other 
plants take the place of the heather, the most widely spread 
being cotton-grass (Hriophorum angustifoliwum and LE. 
vaginatum), spike-rush or Scirpus caespitosus, and various 
species of Sphagnum moss. All these plants grow in deep 
peat sodden with moisture. The highest wet moors are 
often the cotton-grass moors, characterised by the growth of 
one or both species of EZriophorum, on peat rarely less than 
5, often 10 to 15 and even 30 feet in depth and saturated 
with water. Scattered amongst the cotton-grass moors are 
limited areas of Sphagnum moor, also on very wet peat. 
Cotton-grass moors are common in the Pennine range on 
gently sloping plateaux, between 1200 and 2200 feet 
elevation, and on account of their wetness are locally 
named mosses. Peat is being formed at a rapid rate in 
them at the present time. The Scirpus moors are also 
developed on deep peat, which is still being accumulated, 
and is saturated with water at most times of the year. 
The Scirpus is often mixed with a considerable amount of 
stunted heather. The Scirpus moors are very widely spread 
in the north of Scotland, the western Highlands, Hebrides, 
Shetlands, etc., and are common in the Dublin Mountains 
at lower elevations than the cotton-grass moors. Peat is 
also being formed at the present day in the Scirpus moors. 
In the southern Uplands of Scotland and the western 
Highlands, Westmorland and Wales, there are the so-called 
grass moors, which cover extensive areas of badly drained 
glacial till and boulder clay. The dominant vegetation 
consists of moor-grass (Molinia caerulea), mat-grass (Nardus 
stricta), and rush (Juneus squarrosus), growing on a peaty 
acid soil, which is wet during most of the year. A surface 
peaty layer, consisting of a sod six to nine inches thick, 
made up of bases of shoots and rhizomes, rests on an 
impervious subsoil. The grass moor is not a true moor as 
the soil is not pure peat. It is much wetter than ordinary 
hill pasture and has less value for grazing. 
