Port 

 Nolloth 



Cape Cape 

 Point Agulhas 



Cape 

 Padrone 



St. Durban 

 John's 



Fig. 193 Composition of fauna and flora of South African shores 

 between Port Nolloth and Durban, showing the relative propor- 

 tions of the different components. 



A = Warm water element. 



B = South eastern element. 



C = South coast intermediate element. 



D = South west element. 



E = Western element. 



F = Cold water element. 



G = Cosmopolitan element. 

 (After Stephenson.) 



It is suggested that the nature of the response to temperature 

 controls the movements of those plants that migrate down in 

 winter, whilst response to strong insolation determines the be- 

 haviour of those that move down in summer. It is likely that it is 

 the response of the sporeHngs rather than the response of the adults 

 that is involved, though the problem has not been investigated 

 experimentally. 



341 



