CHAPTER VI 



MARSH AND AQUATIC ASSOCIATIONS 



General distribution of the marsh (or swamp) and aquatic associations. 

 Non-calcareous waters. Swamps on the sandstones and shales. Cal- 

 careous waters. Swamps on the limestone. Ruderal marsh species. 

 Reed swamps. The vegetation of quickly flowing streams. Alien 

 aquatic plants. The relation of mineral salts to the flora and 

 vegetation. 



GENERAL DISTRIBUTION OF THE MARSH (OR SWAMP) 

 AND AQUATIC ASSOCIATIONS 



IN the Peak District, as on the Pennines generally, aquatic 

 and marsh associations, and more especially the former, are 

 very meagrely represented. The Pennines, consisting of 

 fissured rocks like the Carboniferous sandstones, and porous 

 rocks like the Carboniferous limestone, have no natural lake- 

 lets or tarns such as occur on the older Silurian and Cambrian 

 rocks. Again, in the Peak District^ there are no extensive 

 alluvial flats; and it is in such situations that aquatic and 

 marsh associations attain a maximum degree of development. 

 From such lowland alluvial deposits, some of the more cosmo- 

 politan aquatic and marsh plants spread up the streams, where 

 they form narrow, fringing associations which are too small, 

 however, to be marked on vegetation maps except such as are 

 constructed on a very large scale. Hence aquatic associations 

 and reed swamps are poorly developed and only of local 

 occurrence on the Pennines. 



In this district, marshes or swamps are characteristic of 

 those spots on the hill-slopes where springs issue, and of the 

 immediate banks of the streams where these banks happen to 

 be flat. Reed swamps are very local; and even when they 

 do occur, they are very small and not very typical. The streams 

 themselves are tenanted by numerous characteristic mosses, 



