COTTON-GRASS MOORS 193 



they are very minute, thus there is little transpiring surface, and 

 the plant is able to do with very little water. Heather is not 

 found on damp peat, but on thin, dry peat. Some Heather-moors 

 are characterised by the abundance of the Bog-Myrtle (Myrica 

 Gale). This is generally found in badly drained situations, as 

 on the clearings of Birch woods, and is often associated with the 

 Cotton-Grass and other marsh-loving plants, such as the Lesser 

 Spearwort, the Bog-Asphodel, Reeds, etc. 



COTTON-GRASS MOORS 



The Cotton-Grass is a Sedge, not a Grass. Sedges, Rushes, 

 and Grasses occur together on moors and have a superficial resem- 

 blance, but may easily be distinguished from each other by the 

 following characters. Grasses have hollow stems which are 

 circular in outline, and their leaves are arranged in two rows 

 alternately ; Sedges have solid, angular stems, with their leaves 

 in three rows ; whilst Rushes have cylindrical, sometimes jointed, 

 leaves, and the perianth of the flower is membranous. In the 

 Cotton-Grass the long cottony filaments represent the calyx and 

 corolla ; within them are the stamens and ovary. The Cotton- 

 Grass requires plenty of moisture, and is therefore found in bogs 

 on moors ; in such situations the Heather disappears. It may be 

 found at the edge of a bog which is drier than the central part 

 of it. When the Heather is the dominant plant in any part of the 

 moor, the plants found with it form what is known as a Heather 

 association ; when the Cotton-Grass is dominant, the plant associa- 

 tion is a Cotton-Grass or Eriophorum association. One of the 

 sub-dominant plants found associated with the Cotton-Grass 

 is the Bog Moss (Sphagnum). Sometimes this moss becomes the 

 dominant plant in cases of extreme moisture, and then the plant- 

 association is a Sphagnum, not an Eriophorum association. Very 

 few plants are found with the Cotton-Grass ; there are often two 

 or three species of this Sedge present in the same bog, together 

 with another Sedge, the Tufted Scirpus. The Common Crowberry 

 does occur, but is not common in Cotton-Grass bogs. At the edge of 

 the bog, Heather may be present. The appearance of a Sphagnum 

 bog depends almost entirely on the rainfall of the year ; it requires 



VOL. IV. 13 



