164 Svb-formation of the Chalk 



recent immigrant or not, it seems that only in the south- 

 east of England has it found climatic conditions enabling 

 it to become dominant and to form woods, beating the 

 ash, its light-demanding competitor on calcareous soils, 

 by reason of the deep shade which it oasts. While the 

 beech has every appearance of being native so far west as 

 Cornwall, and while it flourishes and ripens seed so far 

 north as Scotland, where it is often successfully planted 

 on very various soils, it appears quite unable to form 

 natural woods outside the area indicated\ It may, how- 

 ever, have had its distribution as a wood-former somewhat 

 curtailed by clearance of forest on the outskirts of its 

 present area, i.e. on the chalk escarpment on either side 

 of the Chiltern region, for in Cambridgeshire and Wilt- 

 shire indications of natural beechwoods are not wanting^." 

 We may therefore conclude that the beechwoods on 

 the chalk of southern England represent an extension of 

 the continental beechwoods on calcareous soils '. In this 

 country they occupy the drier chalk rather than the 

 damper marls, a fact which may be connected with the 

 damper climate of England. The factors which have 

 arrested the further progress north-westward of the beech 

 association are not at all clear, since the beech itself, as we 

 have seen, flourishes and sets seed perfectly well far beyond 

 its limits as a wood-former. 



1 "It is interesting to notice that the distribution of certain asso- 

 ciations of land molluscs which show continental afBnities, is limited in 

 a similar way. Helix obvoluta, the most typical species of these 

 associations, is found nowhere beyond the limits of the beech asso- 

 ciation." 



"^ Moss, Rankin and Tansley, 1910, pp. 143 — -1. 



'' Graebner (Die Pflmneiiwelt Detitschlands, 1909) describes the 

 German beechwoods as occupying mostly marly soils. The English 

 beechwoods on chalk must be carefully distinguished from the local 

 beechwoods on sand which belong to the heath formation, and have 

 already been mentioned (p. 102). Both types of beechwood are apparently 

 ooniined to the south of England. 



