THE PLANT ECOLOGY OF THE COAST BELT OF NATAL. 377 



2. Humidity and Pkecil'itation. 



It is unfortunate that no reliable figures for the relative 

 humidity at diffei'ent stations are available. It is undoubtedly 

 uniformly higli for practically the whole coast belt, as is 

 shown by the successful cultivation of the sugar-cane every- 

 where. It appears to vary in a manner parallel to the 

 temperature variations, the stations which show a greater 

 range of temperatures also showing lower relative humidity 

 and less cloudiness. Even the rainfall records are not so 

 satisfactory as they might be, there being frequent gaps in 

 the returns for all the stations except Durban. 



The average annual rainfall in inches and the average 

 number of days in the year on which rain falls are as follows 

 for the various stations : 



J 1 Wet 

 I^^^^^^^- days 



Port Shepstone (on the coast and fully exposed) 48*19 122 



Umzinto (7 miles inland in a valley) . 



Winkle Spruit (on the coast) 



Durban (on the coast) 



Verulam (5 miles inland) . 



Stanger (5 miles inland) 



37-69 90 



45-67 117 



39-7 137 



38-81 111 



39-94 167 



The stations are again arranged in order from south to 

 north. Port Shepstone shows the highest rainfall. It is 

 fully exposed to the rain-bearing winds from the Indian 

 Ocean and a high plateau rises immediately behind it, the 

 coast belt being narrower at this point than anywhere to the 

 north. Umzinto shoAvs the lowest average rainfall. Being a 

 few miles inland and in a valley it is sheltered behind the 

 rising land which lies between it and the coast line. It is 

 therefore drier and, as explained above, it is also hotter, i.e. 

 it begins to show the dry, hot valley-type of climate, though 

 not to the same extent as in the midlands. Durban and the 

 North Coast stations show only slight differences in rainfall, 

 but Stanger is wetter than Verulam and has the rainfall 

 better distributed (167 wet days as against 111). 



