PLANT DISTRIBUTION AND ASSOCIATIONS. xlv. 



afford the only safe footing amid the channels of black peat 

 and the treacherous patches of bright-green bog-moss. 

 Instead of the purple haze of autumn, they furnish a dazzling 

 snow white harvest in spring, and in winter the sombre ling is 

 readily distinguished in the landscape from the green, yellow, 

 and red hues which denote the cotton-grass. 



A pure Cotton-grass moor as on Boulsworth Hill and 

 Jackson's Ridge is composed of Eviophorum vaginatum almost 

 exclusively. The other cotton-grass, E. angustifolium, occasion- 

 ally becomes prominent, but as a rule it is as limited in 

 amount as bilberry, crowberry, and heather. On the slopes 

 however, and on rocky ground, these latter enter more largely 

 into' the association, and in places there may be a good deal 

 of them. The following table shows the relative abundance 

 of the species present : — (i) North of Widdop Reservoir, and 

 (2) on the slopes of Boulsworth Hill and Jackson's Ridge from 

 about 1100ft. to 1500ft. Their presence is indicated by the 

 plus sign, the most abundant ones being distinguished by its 

 repetition ; the minus sign is used for those which are present 

 in only small quantity, or locally in wetter places, and the 

 zero attached to such as are absent. At the same time the 

 position of the plants in the list also indicates their comparative 

 importance. 



It is also possible that Erica Tetvalix occurs in small 

 quantity ; it certainly is not far off at rather lower levels. 

 The strong development of the crowberry is a noticeable 

 feature of this association, as is also the presence of the tufts 

 of blue moor-grass. 



The transition from the grassy moor to the cotton-grass 

 moor may be traced on Langfield Edge, where the slopes are 

 situated on Yoredale shales, and so though they are decidedly 



