72 PRESIDENTIAL ADDRESS SECTION C. 



or forest. The majority of ruderals are excellent, colonisers. They 

 flower profusely and for a long period each year, and form large 

 quantities of seed. Many are annuals, especially m cultivated 

 land. These gradually give way to perennials. Many of the 

 perennials have a creeping habit of growth. Few ruderals, how- 

 ever, can withstand shade, and the taller species kill out the low- 

 growhig. Many ruderals are introduced plants. The Compositae, 

 Solanaceae, etc., are common all over, while the more tropical 

 families, e.g., Acanthaceae. Amarantaceae, are more prominent on 

 the Coastbelt. 



5. — Grassveld. 



The earlier stages of succession in this important type are 

 similar all over Natal, while the later stages differ more in the 

 different areas. Grassveld often is established by a succession 

 from water and wet ground following after "vlei grasses" in the 

 hydrosere already dealt with. The succession on dry soil and rocks 

 ^i.e., in the xerosere) is as follows: — 



A. Lithophytes. Blue green Algae, Lichens, Mosses and 

 petrophilous flowering plants, Crassula spp., Gyperus rupestris, etc. 



B. Chomophytes or crevice plants. A large class, since prac- 

 tically any seed may germinate in rock crevices. Certain species, 

 however, are distinctly characteristic of such situations, e.g., many 

 Compositae (especially at higher altitudes) and bulbous Mono- 

 cotyledons. Chomophytes may be (a) Exposed (often cushion 

 forms or spreading), (b) Sheltered (including most of the bulbous 

 species), (c) Shade (Streptocarpus spp., etc.), or (d) Hydrophilous 

 (growing on dripping crags). 



C. Primitive Grassveld. Species of Aristida, Eragrostis, 

 Sporobolus, etc., which are bunch grasses with deep roots or 

 Gynodon dactylon and other creeping forms which root at the nodes. 

 All are light demanders and good colonisers. 



D. The sub-climax and climax stages of grassveld. These 

 gradually displace the pioneer species or follow after vlei grasses. 

 Separate types in the different areas must now be distinguished. 



1. Midland Grassveld. Of this there are two distinct sub- 

 types, viz. : (a) High Veld, with The in ed a triandra, var. glauca 

 dominant and A ndropogon hirtus and other species often sub- 

 dominant. Invasion by species of Acacia and other pioneer trees 

 leads to the establishment of Thorn Veld. 



Mixed with the grasses are a great variety of associated plants 

 which form (a) Vernal Aspect Societies, consisting mostly of either 

 monocotyledonous or dicotyledonous geophytes with underground 

 storage, the spread of which is favoured by grass-burning, or (b) 

 Autumnal Aspect Societies, shrubby species which grow with the 

 grasses, are kept in check by grass-burning and often represent 

 transitional types to scrub and forest. 



2. Coastbelt Grassveld. This is distinguished by the presence, 

 though not by the dominance, of distinctly tropical species, e.g., 

 PoUinia villosa, Perotis latifolia, Fogonarthria falcata, and 



