318 l^ra/isactions. 



depended rather on edaphic than cUraatic conditions — i.e., on 

 subsoil water rather than number of rainy days. 



The above rain-forests are not, strictly speaking, " coastal. "^ 

 but are merely the ordinary lowland forests of the particular 

 locality. But their seaward margin is frequently distinctly 

 modified by coastal conditions. Thus, there may be a dense 

 growth of shrubs or low trees, as originally pointed out by 

 Hector (21), forming a definite plant-association or maybe for- 

 mation, which at times exhibits a zonal arrangement of its 

 members, defined by their wind- or spray-resisting powers, the 

 trees or shrubs being gradually more xerophytic from within 

 outwards. In other places Phormium tenax may form a natural 

 wind-break between the forest and the actual shore, reaching 

 so close to the water that seaweed and pieces of driftwood may 

 be stranded at its base. 



Certain edaphic formations are not affected by the rainfall. 

 Thus the dunes at Martin's Bay, in the very centre of the wet 

 region, maintain clearly their_ desert character, while at the 

 head of the western sounds far inland in the heart of vast forests 

 are muddy flats covered with the usual halophytes. With rock 

 formations, on the other hand, it is quite the contrary. These 

 vary much in their plant covering according to the rainfall. On 

 the dry east coast, masses of the succulent Mesembrianthenmm 

 australe depend from rock-crevices and alone hide in a few places 

 the bareness of the surface. But in the west great walls of rock 

 are covered with arborescent plants, the constant wet being 

 most favourable for peat-production, which, lodging on ledges 

 and in hollows, forms a thin soil, which the plants can use,, 

 thanks to the far lateral spread of their roots. Between such 

 fertile cliffs and those of the east there are manj transitions in 

 harmony with the water conditions of the station. 



4. Dunes, Salt Marshes, and Salt Meadows. 

 The absence of uniformity in the coastal formations, as 

 mentioned previously, is not without some striking exceptions. 

 Such are found in the case of those before-mentioned formations 

 which depend on some special edaphic rather than chmatic in- 

 fluence. Of these, the most common are dune, salt-marsh, and 

 salt-meadow formations. Not only are dunes, salt meadows, 

 and salt marshes remarkably uniform throughout the Soutli 

 Island, but through nearly the whole of the New Zealand biolo- 

 gical region — a sandhill in the north of Auckland, for instance, 

 not differing much from one of the extreme south of the South. 

 Island, Stewart Island, or even of Chatham Island (12 ; p. 259 

 et seq.). To find a dune floristically and even ecologically dis- 

 tinct one must visit the Auckland Islands, whose sandhills- 



