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 (^oc. 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 Rliyi^cospora 

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

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



