THE VECtETATION OF NATAL. 321 



this in common with the valleys, however, that in winter 

 they have a much lower temperature than tlie surrounding 

 veld. Frosts are common in all the midland vleis. 



The vegetation varies (1) according to the amount of water 

 present, and (2) according to the degree of stagnation of the 

 water. There are vleis which are formed simply by a 

 streamlet spreading itself over a iiat level surface. The 

 water drains through fairly quickly. Such a vlei is driest 

 towards the sides and wettest towards the centre. Other 

 vleis are small circular depressions. They are usually dried 

 up during the dry season, and wet during the rainy season. 

 The water in them becomes stagnant. Actual lakes are not 

 at all common, and very few reach an acre in extent. 

 They do, however, occur in small depressions up to an 

 altitude of 4000 feet. In many of them surprisingly iew 

 aquatic phanerogatns occur. 



The following lists of types include some of the commonest 

 plant associations found iir the marshes : 



1. Dominant. . Andropogon nardus var. margi- 



natus and Andropogon filipendu- 

 lus. 

 Sub-dominant. Setaria aurea and Cyperus latifo- 



1 i u s . 

 This is the driest type of vlei. Soil moist and alluvial. 



2. Dominant. . Ischasmum fasciculatum var. arc- 



t u a t u m . 

 Sub-dominant. Setaria aurea. 



Here the soil is again moist and alluvial, but a stream 

 flows through the middle of the marsh. 



o. Dominant. . Setaria aurea and Eragrostis nebu- 

 1 o s a . 

 Sub-dominant. Andropogon nardus, A. filipen- 



d u 1 u s , C y p er u s s p p . 

 Another of the drier types. 

 4. Dominant. . Cyperus latifolius and Erianthus 

 capensis var. villosa (see PI. XXIII, 

 fie-. 1). 



