Botany 



57 



THE CHALK FORMATIONS 



I. Grassland 



The wide stretches of Chalk grassland on the North and South Downs and 

 on Salisbury Plain are such a uniform and well-characterised community 

 that the Chalk grassland of Cambridgeshire cannot fail to have special 

 interest. Comparatively little of it remains untouched by cultivation, but 

 parts of Newmarket Heath, the Gogmagog Hills, and Royston Heath 

 (just outside the County) are still more or less natural. The old Roman 

 road (the Via Deuana), the Devil's Dyke, and the Fleam Dyke (see Figs. 20 

 and 21), are now also clothed with grass communities and bear most of 

 the typical and some of the rare species of chalk grassland. 



A rough indication of the composition of the plant community can be 

 gained from the following group of species collected in an area of a few 

 hundred square yards on Royston Heath. It was obtained by a student 

 class, and represents the results of twenty-nine random throws of a quadrat 

 of one decimetre square. The species are listed in order of the frequency with 

 which they occur in the twenty-nine samples ; the figure after each species 

 shows the number of quadrats in which it appeared; the letter before it 

 shows its life-form in Raunkiaer's terms (H = Hemicryptophytes — buds in 

 surface layers of soil; Ch = Chamaephytes — buds close above ground; 

 G = Geophytes — buds below soil; Th=Therophytes — annuals). 



In view of the very small area examined, it is extraordinary how closely 

 this corresponds to Chalk grassland examined by Tansley and Adamson on 

 the South Downs: of the fifteen most constant species given by these 

 authors, fourteen are represented above. Many other highly characteristic 

 species are to be found in other parts of the grassland on Royston Heath; 

 among them are the following: Leontodon hispidus, Avetia flauescens, 

 Galium veriim, Priiiitila veris, Carlina vulgaris, Polygala vulgaris, Daucus 



