MARINE ALGAL VEGETATION 



117 



It is usually the case that it is the older parts of the fronds 

 which are most covered by epiphytes; this agrees well with the 

 fact that the older fronds have a rougher surface than have the 

 younger ones, and therefore retain the spores better. The epiphytes 



Fig. 7. Polysiphonia fastir/iata on Ascophylluin which is hanging on the face of the rock. 

 Reykjavik, Aug. 13, 1909. (From phot, by Hesselbo.) 



on the Fucacece do not appear to arrange themselves in strata as 

 do the LamrnaWa-epiphytes. 



The intermingled species do not play any special role in 

 the Fucus -belt, as regards the vegetation; they consist partly of 

 species which grow on the Fucacece and partly of species which 

 ordinarily grow outside the Fucus -belt. Of these species the fol- 

 lowing may be mentioned: — 



