168 VEGETATION OF THE PEAK DISTRICT [CH. 



THE FEN FORMATION 



In the lowlands of eastern England, peat occurs which is 

 characterized by alkaline waters, and by a high, soluble mineral- 

 content, especially by a high lime-content. Such peat bears a 

 totally different set of plant associations and societies and quite 

 a different flora; and its vegetation must therefore be placed 

 in a different formation. The peaty tracts of eastern England 

 which are characterized by alkaline waters are usually spoken 

 of by the local inhabitants as " black fens " or simply " fens " ; 

 and the difference between the two types of peaty vegetation 

 appears to be of a very fundamental nature. Accordingly, the 

 vegetation of acidic peat may be said to belong to the moor 

 formation and that of alkaline peat to the fen formation. 



"HOCHMOOR" AND " FLACHMOOR " 



Continental plant geographers distinguish two main types 

 of peat vegetation under the names of " Hochmoor " and 

 " Flachmoor." In Warming's Oecology of Plants (1909 : 204), 

 these terms are represented by " high moor " and " low moor " 

 respectively. These, distinctions do not entirely correspond to 

 the distinctions of moor and fen adopted by most British plant 

 geographers. Warming (loc. cit.) gives nine distinctions between 

 " high moors " and " low moors." 



1. "Low moor arises on a surface that is covered with 

 water.... High moor arises on moist soil or even above water." 

 On this basis, the moors of the Peak District are " high moors." 



2. "Low moor has a flat surface (either horizontal or 

 inclined). High moor has a convex surface." The cotton- 

 grass moors of this district have, on the whole, a flat surface ; 

 and, therefore, if judged from this point of view alone, they 

 would have to be placed among " low moors." 



3. " Low moor is produced particularly by grass-like plants, 

 including Cyperaceae.. . .High moor owes its origin to bog-mosses, 

 Sphagnum and others, and includes many Ericaceae." Apply- 

 ing this test, the heather moors would be placed among the 

 " high moors," the cotton-grass moors among the " low moors " ; 

 but this test for low moors is unsatisfactory, as Warming 

 (p. 202) also includes " grass-like plants," such as Rhyncospora 

 alba, Carex spp., Eriophorum spp. (especially E. vaginatum), and 

 Agrostis canina, among the constituent plants of " high moor." 



