222 The Flora of the Cambridge District 



land is in the meadow zone, partially in it, or in the moor 

 zone. The occurrence of the Saxifrage in such patches 

 produces some extraordinary mosaic effects of colour in earlv 

 summer. The ridges which are very irregular arc a pure 

 white, the hollows a deep green with grass and rushes. 



In some places, as near Holy well, depressions in the sandy 

 common are lined about a yard broad with white Saxifrage ; 

 this ribbon follows the windings of the banks, occasionally 

 spreading over some low spur (first zone) ; below comes the deep 

 green of grass (Agrostis), Rush and Potentilla palustris (second 

 zone). Along this Suffolk border however the fen lias dis- 

 appeared and is represented by bean and potato fields or 

 corn fields. 



In Dernford Fen, south of Cambridge, the same may be 

 observed. 



2. The Dry land. 



The lands lying above the level of the fens, either as 

 isolated spots, islands, or as part of the system of hills to the 

 south, are coloured pink, yellow and brown in the map. The 

 whole represents a slightly xerophytic group of plants corre- 

 sponding to the dry Germanic group and its associates already 

 mentioned. This portion is characterised by light soils, chalk 

 and gravel, and in West Suffolk by sand. Trees are rare 

 and are generally planted in the form of wind-shields. Beech 

 on the chalk and conifers and beech mixed on the sands of the 

 Mildenhall district. 



The planted trees alone, apart from other changes in the 

 flora, would give a clue to the general division of this portion 

 of the district. 



In the west, Gorse and Bracken are rare, Calluna, Erim 

 probably not found, and Carex (trcinir'm is absent ; hut the>e 

 are characteristic of the eastern portion, whilst Antrmjnhi* 

 danicus, Linum perenne, Ain'inoiic /'///.sv////A/, Efeliantktmwn 

 chamaecystus, Tnfnlhnii <H-lir<>l<>ti<-<i, r<>lii<j<il'i c<tlcr<u are 

 typical of the chalk downs, and Carum Bulboca*t<tnum, /<V- 



