38 
Transactions of the Royal Society of South Africa. 
The soil is essentially uniform throughout the area, being a fine red- 
brown loam, containing comparatively few large particles or stones. On 
mixing with water in a tall glass jar the whole of the solid matter settles 
within twenty-four hours, leaving only a slight opalescence, due probably 
to the presence of a small quantity of colloids. The soil tends to become 
caked and hard during dry weather after rain. 
No marked differences in climatic or edaphic factors distinguish the 
Sketch map to show position of Manubie and surrounding country. 
woodland from the savannah, though these are of strikingly different 
appearance and are separated by a sharp boundary line. 
The sharp line separating the two associations may well be due to old 
bush fires, on the site of which savannah regenerated. The woodland has 
the appearance of being the final closed association within the district, and 
the savannah, here as elsewhere, has the appearance of an intermediate 
association, though it may actually be of great persistence and permanency. 
After the ground has been cleared by a bush fire, regeneration takes place 
very rapidly, and the ground is speedily covered with a dense growth of 
interlacing rhizomes and tall grasses in which further germinations are 
