AN (ECOLOGICAL SURVEY OF THE MIDLANDS OP NATA[;. 537 



found occasionally mixed with the Andropogon species or 

 with the other associations. 



(e) Of trees and shrubs the following are common close to 

 the river side : 



Zizyphus mucronata, Trema bracteolata, Ficus 

 capensis, F. natalensis, Rubus rig-idus, Eugenia 

 cordata, Rhus spp., Acacia caffra, Celastrus buxi- 

 folius, Lippia asperifolia, Royena pallescens, 

 Randia rudis, Ehretia hottentotic a, Combretum 

 salicifolium. They grow closer together than in the rest 

 of the thorn veld (Pis. XL, XLII, XLIII). 



In other parts of the low veld region, where the streams 

 and rivers have formed steeper banks and cliffs, we find the 

 I'ocky hillside formation already described. The streams and 

 rivers, as followed along their courses, show examples there- 

 fore of nearly all the types of plant formation found in the 

 area — bush, veld, vlei, and rocky hillside formation. It is 

 only in the aquatic or semi-aquatic plant associations of their 

 margins that they show a distinctive type. Natal is rather 

 poor in purely aquatic plants as distinguished from the marsh 

 plants that are often semi-aquatic. 



The fresh-water algse have not, as far as the writer knows, 

 been much collected or described. Nitella sp. is abundant. 



8. PLANTATIONS. 



(1) Wattle. 



In Natal the culture of the black wattle (Acacia mol- 

 lissima) has become one of the most important industries. 

 Its bark is particularly rich in tannin and it is being more 

 and more used for tanning. The tree is a native of Australia 

 and was first introduced into Natal probably as an orna- 

 mental tree. The first bark was sold locally in 1884, and the 

 first consignment was sent to Europe in 1887. Ac present 

 the annual value of Wattle bark exported has gone up to 

 over £200,000. The timber is also used as mine props. The 

 industry is rapidly growing in importance. 



