AN (EC0L0C41CAL 8UKVEY OK THE :MI1iI,AN1»S OF NA'l'AL. 487 



stability and instability in the habitats, and in the plant 

 formations, has been found useful for obtaining a broad 

 grasp of the essential features of the vegetation in any 

 defined area. 



At first the grass associations of the veld, varying and 

 changing as they sometimes do every few yards, appeared 

 hopelessly confusing. Nevertheless, where definite plant 

 associations were found to cover an area of any size, and 

 the conditions were carefully examined, it was always found 

 that they were more or less uniform over that area, and this 

 uniformity was the result of a comparatively stable topo- 

 graphy. Also, where great variation in the plant associations 

 occurred, it was always seen that there was an equally great 

 variation in the soil conditions, brought about by the fact 

 that soil transportation and denudation were going on Avith 

 greater rapidity. To put it briefly, the more definite types of 

 plant formation occupy the geologically stable and more or 

 less even ground, while the more variable types are found on 

 the broken ground. It is therefore possible to distinguish in 

 the veld formation (using the nomenclature adopted by the 

 oecologists mentioned above) a subformation of relative 

 stability — in natural veld it mostly consists of a single, almost 

 pure association of Anthistiria imberbis — and a subforma- 

 tion of relative instability made up of a variety of associations. 

 It is well to keep in mind, however, the fact that these terms 

 are purely relative. In Natal, where surface changes are 

 proceeding everywhere with extreme rapidity, what has been 

 called stable formation might be regarded as unstable if com- 

 pared with similar formations in other countries. 



It must, of course, be admitted that though these terms are 

 useful for stating certain facts in a concise form, yet as far 

 as real explanation goes they do not take us very far. Geol- 

 ogical changes only lead to alterations in the vegetation in so 

 far as they change the physical and chemical characters of 

 the soil, or the environment of the plant as a whole. Further 

 advance in the study of plant oecology is only likely to be 

 made as a fuller knowledg-e of the environmental factors — 



