xviii TOPOGRAPHICAL REMARKS. 



those plants which are absolutely aquatic have not suffered 

 so greatly as the others; but they are fast decreasing, now 

 that the steam-engine causes even many of the ditches to be 

 dry in summer. As the character of the Fen district is 

 very little known, it is well to remark that the peat is not 

 formed of Sphagnum, like that of bogs, but consists chiefly 

 of the decomposed remains of various aquatic herbaceous 

 plants. At the bottom there is a layer formed mostly of the 

 remains of the woody plants and trees which constituted the 

 forest which formerly covered the country. The remains of 

 oak, yew, hazel and willow are found abundantly in some 

 parts of the Fens, and pine wood is plentiful in others. The 

 wood of the larger trees is often well preserved and turned 

 quite black, but a few inches of the surface have become 

 soft and spongy. The latter is the condition of most of the 

 smaller branches and the lesser ligneous plants. The Rev. 

 Leonard Jenyns informs us that it is the opinion of the turf- 

 cutters at Isleham that, before the present more perfect 

 drainage of the Fen, the turf grew at the rate of about 

 twenty inches in sixteen years. Now the want of sufficient 

 water has put an end to this restoration of the turf in the 

 places where it has been cut for fuel, and what little is ob- 

 tained for that purpose is of very inferior quality to the 

 former supply. The ditches in the Fen and the holes made 

 by the turf-cutters are soon occupied by a few plants, such 

 as Chara hispida, Utricularia vulgaris, Callitriche, several 

 species of Potamogeton, Sagittaria, and Alisma ranunculoides. 

 As soon as these have formed a tolerably firm mass by the 

 decomposition of their lower parts, the Junci, Carices, Cla- 

 dium, and similar plants, establish themselves upon it. It 

 then ceases to increase much in height, but in the course of 



