542 J. w. BEws. 



remnants of largei- bnsh. They are similar in composition to 

 the outer margin of the latter, but are more open and irregular, 

 and this leads to differences in the undergrowth. 



Bush clearinsfs have numerous coarse herbs and shrubs 

 and associated plants of the veld, as well as occasional trees, 

 such as Xymalos monospora, that may have resisted the 

 fire that destroyed the bnsh. These plants gradually become 

 replaced by Andropogon associations. 



(3) The Thorn Veld Formation. 



This occurs in the low veld region. The trees grow 

 isolated, and are prevented from growing closer by the con- 

 stantly recurring grass fires. Their umbrella-form, horizontal 

 root system, variable thorn development, and thick bark 

 are the main features. These are adaptations brought 

 about by their exposure to the hot winds, by the hard, dry 

 soil with shales usually near the surface, and perhaps partly 

 by the annual grass fires. 



(4) The Rocky Hillside Formation. 



In the high veld region this occurs on the slopes which do 

 not face south or south-east. It is intermediate oecologically 

 in its composition, and frequently in its position, between 

 close bush and thorn veld. The trees grow sometimes 

 isolated, sometimes in clumps. The variable soil conditions, 

 particularly as regards moisture, lead to considerable 

 variation in this type. 



In the low veld region on slopes with south exposure thorn 

 thickets are formed of the same composition as the thorn veld, 

 but denser. On slopes with north exposure very xerophytic 

 trees and shrubs (succulents) make up the formation. 



(5) The Alpine Formation, 



On the Zwaartkop mountain the presence of many species 

 not found lower down gives it a distinct character, and 



