Fen Plants 217 



to a variety of reasons, chief among these being an insuffi- 

 ciency of time to go over all the ground, the boundaries of 

 the different areas are too often only approximately correct 1 . 



1. The Fen. 



The great alluvial flats which are known as the fens are 

 for the most part under cultivation ; here and there a rough 

 meadow may be seen, still more rarely a piece of unreclaimed 

 sedge fen. Fields of potato, bean, and corn with their 

 attendant weeds of cultivation are what to-day compose the 

 main flora of the fens. 



Yet even now these expanses differ very considerably from 

 the high land, the place of hedges is taken by ditches fringed 

 with Phragmites, which spreads on either side in the black 

 peaty soil and stands green among the yellow corn. 



Where, as at Wicken, a portion of untouched fen remains, 

 it is possible to see how marked originally must have been the 

 distinction between the fens and the dry land. 



Now that roads have been built and repaired often with 

 chalk, plants foreign to the district are introduced. These 

 flourish only along the roadsides, upon heaps of road metal, 

 and upon the raised road dykes themselves. Such plants as 

 Anthriscus vulgaris, Reseda lutea and Festuca rigida are 

 not uncommon, whilst principally upon the river dykes are 

 Geraneum molle and Caucalis nodosa. Besides these colonists 

 are the weeds of cultivation in the fields, annuals which come 

 and go with the crops. 



The two great distinguishing features which separate the 

 fen from the dry land are the absence from the fen of 

 xerophytic plants such as Hieracium Pilosella and the 

 presence of ditches, which take the place of hedges. This 

 change can be well seen on the western side of the Wicken 



1 The map published with this paper is far from complete; it only 

 serves to indicate the broader features and, it is hoped, will lead others 

 to take an interest in the vegetation of Cambridge and so to complete, 

 what has hardly been begun, a true Botanical Survey of the district. 



