THE PLANT ECOLOGY OF TKE COAST JJIiLT OF NATAL. 441 



therefore, as well as in its floristic composition, it shows 

 marked tropical affinities. Wallace goes on to suggest that 

 the mixed character of tropical forest is due to the extreme 

 equability and permanence of the climate. " Every form of 

 vegetation has become alike adapted to its genial heat and 

 ample moisture, which has probably changed little throughout 

 geological periods ; and the never-ceasing struggle for exis- 

 tence between the various species in the same area has 

 resulted in a nice balance of organic forces, which gives the 

 advantage now to one, now to another species, and prevents 

 any one type of vegetation from monopolising territory to the 

 exclusion of the rest." 



This doubtful explanation might be applied (if it applies at 

 all) rather to explain the mixed character of climax forest, 

 but the scrub is still more mixed, and this is due largely to 

 the fact that it is not a climax, but an intermediate type, 

 wherein competition between the various species is very keen, 

 and only lapse of time is necessary for the suppression of 

 many of them. Fewer species can act as pioneers, so the very 

 earliest stages often contain fairly large and relatively pure 

 consocies, which gradually become more mixed by the invasion 

 of other species. 



In addition to the large number of climbing plants already 

 referred to, including woody lianes with watch-spring tendrils 

 (Dalbergias), there are other general features illustrating the 

 subtropical nature of coast scrub. The species are all ever- 

 green of course, even those with a wider range, which may be 

 regularly deciduous on the Drakensberg. The leaves are 

 either fairly large, rather thick, smooth, symmetrical and 

 glossy, or much subdivided, often finely pinnate — all characters 

 which agree with tropical forest. Epiphytes are not very 

 abundant, but a dozen or more occur (see under Orchidaceas 

 Scrophulariaceae, Piperacete). Parasitesare aboutequally 

 represented (see under Loranthacese, Convolvulaceas,, 

 Scrophulariaceae) . Cauliflory (stem-flowering) is seen in 

 Halleria lucida and Rawsonia lucida, Ficus capensis, 

 F. sycomorus, Schotia brachypetala, Cyclostemon 



