7 
illustrated by the South African Flora. 
What does fall is usually summer rainfall, but whole years may pass without 
any. The average temperatures are lower than at corresponding latitudes 
on the eastern side, owing to the absence of the warming influence of the 
Mozambique current. The region becomes moister and more tropical 
towards the north and east. The soil is mostly sandy or stony. Vegeta- 
tion of scattered xerophytes in the driest parts, passing first into Aristida- 
veld and then into more mesophytic grass-veld and tree-veld in the moister 
eastern and northern portions. 
2. Central Karroo region. The rainfall is small in amount ( 3-14 inches) 
but more regular, increasing in amount from west to east. General altitude 
from 1*800 to 2,500 ft., but the mountains which form the escarpment of the 
central plateau are from 4,000 to 8,000 ft. high, running from west to east. 
These have many species belonging to south-western or eastern genera. 
The temperature of the Karroo shows extremes of heat and cold, with 
frosts in winter. It forms a climatic barrier of considerable importance 
between south-west and east, and it would be still more important were it 
not for the mountains that cross it. The Karroo soils are hard-baked clay, 
very rich in salts. The vegetation is composed of dwarf shrubs and 
succulents. 
3. Cape or South- Western region. Winter rains and dry, hot summers. 
Annual rainfall 20 to 40 inches. In places the rainfall amounts to 60 inches 
or more and the summer heat and drought is tempered by south-eastern 
mist-clouds. Temperatures, except during the summer months, fairly low, 
but actual frosts, except at high altitudes, are not common. Soils varied. 
Dominant vegetation of sclerophyllous shrubs with patches of eastern forest 
in moister situation. Flora shows affinities with South-West Australia, 
and also, to some extent, with the Mediterranean and Europe, though the 
species in nearly all cases are distinct. 
4. Sand-veld Region of the Kalahari. Summer rainfall increasing 
from about 10 to 20 inches from west to east. Temperature considerably 
higher, becoming tropical towards the north. Sandy soil or sand-dunes 
with underground drainage. No surface water. Vegetation of grass-veld 
passing into tree-veld. Flora with close eastern or tropical affinities. 
5 . Dry Thorn-veld {Low-veld) and Succulent Scrub Areas of the 
Eastern side. Summer rainfall 20 to 30 inches. Great extremes of 
temperature. Very hot in summer, regular frosts in winter. Hot winds an 
important feature. Soils dry-baked clays, rich in salts (cf. the Karroo, 
which these areas resemble in many respects). Vegetation of grass- 
veld, tree-veld, succulent and thorny scrub. 
6. High-veld and Mountain Areas of the Eastern side. Summer 
rainfall 30 to 50 inches and also mist-clouds. Temperature range (both 
daily and yearly) not so great as in the low-veld of the valleys, but frosts 
in winter are experienced outside the forests. Soils loose, deep, well- 
