344 



A quatic Societies 



cover, and that support a considerable variety of more 

 scattering species. One of the most widespread of 

 these secondary forms is the beautiful marsh fern, 

 whose black rootstocks over-run the tussocks of the 

 sedges, shooting up numberless fronds. Scattering 

 semi-aquatic representatives of familiar garden groups 

 are the marsh bellwort (Campanula aparinoides}, the 

 marsh St. John's wort (Hypericum virgiuiciim) and the 

 marsh skull-cap (Scittellaria galericulata] : these are 

 dwarfish forms, however, that nestle about the bases of 

 the taller clumps. With them are straggling prickly 

 forms, such as the marsh bedstraw (Galium palustre), 

 the white grass (Leersia) and the tear-thumb (Polygo- 

 num sagittatum, fig. 202). Strong growing forms that 

 penetrate the marsh cover with stout almost vine-like 

 stems are the marsh five-finger (PoteutiUa fxilnstris) the 



FIG. 203. A marshy pool with flowers of the white water crow-foot rising 

 from the surface. 



