494 J- w. BEWS. 



conditions are more stable and the plant formations are con- 

 sequently more definite. 



2. Climatic Factors. 



In the case of the climatic factors there is an equally great 

 variation, and they are equally important. These have been 

 more fully dealt with in the preliminary paper already 

 published, so in this place the following- summary will suffice. 

 The high veld region receives much more deposition of 

 moisture, both in the form of rain and mist ; its southern and 

 south-eastern slopes are sheltered from the dry, hot winds 

 which always blow from the north or north-west ; it does not 

 have such extremes of temperature, being cooler during the 

 day and warmer during the night, cooler in summer and 

 warmer in winter ; it suifers comparatively little from frosts, 

 especially inside the bush. 



The low veld region is very dry, for the rain-bearing clouds 

 tend to pasB over it without depositing much of their moisture 

 until they strike the hills. During the winter — when there 

 is usually a still atmosphere — the cold air sinks into the 

 valleys, and the temperature is therefore lower than on the 

 hills ; a cold frosty mist forms at night over the low veld. 



These climatic factors not only affect the vegetation directly, 

 but they also influence the edaphic factors. Since the higher 

 regions receive more rain, the soils are more leached, and 

 transportation of soil is greater. At the higher regions the 

 soil water dissolves salts from the soils. At the lower levels 

 accumulation of alluvium takes place, and there is also 

 chemical precipitation. As a result the high veld soil is pooi'er 

 chemically, but richer mechanically than the low veld soil. 



In the end of winter, when everything is very dry, the hot 

 dry winds blow down the fine dust from the higher regions 

 to the lower. After the gi-ass is burned the ashes are also 

 blown down in the same way, and this must lead to a further 

 impoverishing of the high veld soil and a corresponding 

 enriching of the low veld. 



