THE VEGETATION OF NATAL. 257 



generally are also extremely poor in phosphates. Iron is 

 very abundant, and where the soil is not well aerated it exists 

 in the protoxide form Fe 0. 



On the higher levels this soil is loose and fi-iable, and when 

 it becomes dry it forms a fine dust. It is red or brown in 

 colour owing to the large quantity of iron it contains. The 

 surface layers, however, are often much darker in colour. 

 Where exposed this soil tends to get blown down into the 

 valleys by the wind. It is a good soil mechanically, well 

 aerated, and suitable for tree growth where other conditions 

 are favourable. It is poor in available plant-food, and the 

 ordinary cereals will not grow on it without manuring. As 

 will be shown later, it is covered with tall grass veld, with 

 forest on the sheltered slopes, and in the smaller valleys. 

 (PI. XX, fig. 1). 



At the lower valley levels the soil is a stiff heavy clay, 

 which becomes dry and baked. It contains nodules of lime 

 or dolomite, as well as a greater proportion of the valuable 

 mineral constituents of the basic igneous rocks. Limonite 

 nodules are also abundant in places. Further, the organic 

 constituents are relatively high. 



The soil is dark in colour. It is a rich soil chemically, but 

 owing to its compact hard clayey nature, its lack of proper 

 aeration, and its great dryness, which is due partly to the fact 

 that the lower valley levels get less rain, the plants found on 

 it are of the most extreme xerophilous character. After it 

 has been properly cultivated and aerated by exposure, it 

 raises rich crops, e.g. of maize. 



The larger particles are seen to be water-worn, and the soil 

 is therefore shown to have been washed down from the higher 

 levels. It is the soil of the Thorn Veld (PI. XX, fig. 2). 



It must not be inferred that all soils in this wide area can be 

 referred to the two types above mentioned. There are endless 

 local variations. On the tops of the kopjes, for instance, the 

 soil may either be washed away almost entirely, leaving bare 

 boulders of rock, or the heavier oxides of iron and larger 

 particles of silica may be left behind giving a hard sandy soil. 



