390 J. W. LEWS. 



dominant over small ni-eas — i.e. those forming definite 

 societies or small associations — are common to liotli. As is 

 illustrated diag-rammatically in text-fig. 4, the main seres 

 lead up to forest of one kind or another^ and consequently 

 most of the coast belt vegetation might be considered as one 

 plant formation. The climate of the coast belt is sufficiently 

 uniform to permit of this view with the exception of the 

 portions where thorn veld is developed, with species of 

 Acacia dominant. Though isolated thorn trees occur at 

 various places on the south coast, true thorn veld only 

 becomes a dominant type from Vei'ulam northwards wliere 

 the climate is drier and hotter. In the midlands thorn veld 

 and thorn scrub fill the river valleys, while forest clothes 

 the south-eastern slopes of the hills above. On the coast 

 belt the position is reversed, the mesopliytic or hygrophilous 

 forest occurring in the sheltered valleys, while thorn veld is 

 found on the more exposed and drier ridges. With slightly 

 moister conditions, howevei', the same class of thorny scrub 

 (e. g. in Zululand beyond the umFolosi and St. Lucia Bay) 

 can be seen to be a stage in the succession to forest, to winch 

 it readily gives way. Tree veld progresses towards scrub by 

 the clumps of trees growing closer and closer together. The 

 mangrove type has many of the appearances of stability, but 

 as the mud-level is raised and the water ceases to bebi-ackish 

 — to a large extent a direct effect of the vegetation itself — 

 the mangroves give way immediately to other trees of the 

 scrub or forest. There is no intermingling in this case. 



Since many of the common coast species have been illus- 

 trated by Medley Wood in his ' Natal Plants,^ and for some 

 time to come the identification of South Africnn plants must 

 remain a matter of difficulty, it has been thought useful to 

 indicate in the following pviges those species thus illustrated 

 by giving the number of the plate after the names. 



1. The Stuand Vegetation. 

 (The initial stages of the psammosere, PI. XXII, fig. 1.) 

 On the belt of shiftino- sand between the sea and the line 



