THE VEGETATION OF NATAL. 297 



The sand-dune bush forms a fringing belt from a quarter 

 to half a mile in width along practically the whole coast-line 

 of Natal. At Port Durnford, Zululand, it begins to extend 

 further inland till at Cape St. Lucia and northwards it 

 reaches forty to fifty miles from the sea. Here, however, its 

 character changes somewhat, new species coming in, such as 

 L a n d o 1 p h i a s , and A c a c i a s p p . 



This is the Littoral Psammophilous Bush as named by 

 Warming, and, as he points out with regard to similar bush 

 in other parts of the world, it is difficult to say whether its 

 xerophytic character is due mainly to the qualities of a sandy 

 soil, or to its salinity, and to the proximity to the sea. In 

 seeking an answer to the question, it should be borne in 

 mind that the soil is kept moist by frequent precipitation, 

 and also by soakage from behind, and the water is not salt. 



(3) LAGOON TYPE—MANGROVE FORMATION. 



The sand-dune bush is interrupted at the river estuaries. A 

 very good example of the lagoon type of vegetation is seen 

 in Durban Bay, into which the Umbilo and Umhlatusan 

 empty their w^aters. Mud is deposited over the lagoon, and 

 a swamp is the result, with the water salt or brackish. In 

 this place we get a Mangrove vegetation, which is an in- 

 teresting outlier of the Eastern Mangrove Flora. It is 

 not very rich in species, consisting only of Avicennia 

 officinalis, Rhizophora mucronata, and Bruguiera 

 gymnorhiza (PI. XIV, fig. 2). 



A Salicornia-Chenolea association occurs on 

 the mud-flats. It consists of Salicornia herbacea and 

 Chenolea diffusa. The Salicornia grows further out, 

 and it is soon followed by the Chenolea, and the two 

 together form dense clumps, which extend in among the 

 Mangrove trees. The breathing roots of the latter often 

 stand up through the Salicornia and Chenolea (PI. XIY, 



