ECOLOGICAL FACTORS 



353 



Pringsheim (1923) and Zaneveld (1937) have both shown that 

 the water loss of the four species is very great, especially during the 

 first 18 hours (cf. fig, 203). Fucus spiralis f. platycarpus loses its 



TIDE 

 LEVELS 



M.H.VV.S. 

 M. H.W.N. 



M.L.H.W.N. 

 M.H.L.W.N. 



M.L.W.N. 

 M.L.W.S. 



M.E.L.W.S.- 



I O WIGHT. 

 S M , B AKER 



? A V 



WEMBURY 

 CQLMAN 



LEI DAM 

 ZANFFELD 



TKick-ness 



Thickness 

 100 



'Increasing Cong. 



4 hrs. 



Fig. 202. A, distribution of Fucaceae on various coasts in relation to the tide 

 levels. M.H.W.S. =mean high water mark spring tides, M. H. W.N. = mean high 

 water mark neap tides, M.L.H.W.N. =mean low high water mark neap tides, 

 M.H.L.W.N. = mean high low water mark neap tides, M.L.W.N. = mean low 

 water mark neap tides, M.L.W.S. = mean low water mark spring tides, 

 M.E.L.W.S. = mean extreme low water mark spring tides, M.S.L.=mean sea 

 level, N.A.P. = Amsterdam tide datum line. B, decrease in diameter of cell walls 

 when placed in sea water of increasing concentration. C, decrease in diameter of 

 cell walls under normal conditions of exposure. An = Ascophyllum nodosum, 

 Fp = Fucus platycarpus, Fs = Fucus serratus, Fv = F. vesiculosus. (After Zanefeld.) 



water the slowest of all, and a definite increase in the rate of water 

 loss can be observed with the different species as each occupies a 

 successively lower zone on the shore, but it must be noted that 

 F. spiralis f. platycarpus ultimately loses a higher percentage of 

 water than the other three. Haas and Hill (1933) also showed that 



C S A 



23 



