Chalk Scrub 171 



the felling of the yew trees would be likely to 

 arrest it. 



The explanation given is in accordance with the 

 observed facts, but at present it lacks corroboration or 

 direct verification. It is possible that other factors are 

 operative, and it may be that the habitat of the yew- 

 wood really differs from that of the beech wood, though 

 we have no clue to such a difference. 



Scrub association. On the outskirts of beech woods and 

 scattered on the chalk generally, but more especially 

 occurring in old chalk pits, by the sides of trackways, and 

 often left to form natural hedges, e.g. between the culti- 

 vated ground and the open chalk pasture, a very 

 characteristic scrub occurs, consisting of a considerable 

 number of species of shrubs, many of which are found 

 chiefly or almost exclusively on calcareous soils (Plate 

 XX). 



It is noteworthy that some of the most abundant 

 species of this scrub are also the dominant shrubs of- the 

 clays and loams and of the sands, sandstones and shales, 

 e.g. Cratsegus monogyna and Prunus spinosa. On cal- 

 careous soils, however, many other species, which are rare 

 or almost absent on the non-calcareous soils, are abun- 

 dantly associated. 



A characteristic feature of the chalk is the abundance 

 of species of Rosa. The fruticose Rubi, on the other 

 hand, are neither so abundant nor so rich in species as on 

 the sand. The Juniper (./. communis) is abundant in 

 places and forms a most characteristic open scrub of stiff 

 erect bushes almost black in colour and often several feet 

 high. 



The following shrubs and climbers occur : — 



