6 5 6 



ZONES AND REGIONS [Pt. Ill, Sect. II 



3. HEATH 1 . 



Heath is represented in a typical form and over larger tracts in cold tem- 

 perate Europe alone, particularly in the west and north-west. Its presence 

 is determined by the social occurrence of Calluna vulgaris, which except for 

 a few stations in North America is confined to Europe, and even there 

 attains any considerable significance only in districts with a maritime 

 climate. Other Ericaceae partly occur as accessory constituents of the 

 heath, but they form no independent heath-formation. 



Fig. 398. Littoral vegetation of South Island of New Zealand. Dunes near New Brighton. 

 Right hand : Coprosma acerosa, A. Cunn. Left hand : Cassinia fulvida, Hook. f. On the dune : 

 Desmoschoenus spiralis, Hook. f. From a photograph by Cockayne. 



Calluna vulgaris,, the common ling or heather, forms the chief constituent 

 of the vegetation over large tracts of country, both sandy and moory stations, 

 provided the soil be very poor in lime. The sandy soil, on which Calluna 

 has settled, soon acquires a coating of acid heather-peat, so that the ultimate 

 chemical difference between the two substrata is not great. The soil of the 

 moor is indeed physically Avetter than sandy heath soil, but free humous 

 acids render it physiologically dry. Peat and sand are very poor in mineral 

 food, and this circumstance assists the Calluna, for, according to Gracbner, 

 its roots thrive only in extremely weak nutritive solutions, whereas most 



1 See Graebner, op. cit. 



