MARINE ALGAL VEGETATION 



91 



upper littoral zone, but not known below the limit of low-tide I 

 have also designated semi-littoral as they might be expected to 



grow lower down. 1 



C. The Sublittoral Species. 



These species play the principal role in the sublittoral vegeta- 

 tion. This may be characterized in a somewhat similar manner as 

 the vegetation of the upper littoral zone, although conversely as 

 regards red and green algae, viz. by a large number of red algae 

 and an extremely small number of green algae and by the occur- 

 rence of a mass of Laminariacece. In Table 7 , these species are 

 marked with an s before the name. Their number is shown by 

 the following figures: — 



Red 2 



Brown 



Green 



Blue-green 



Total . 





Species 





Littoral 



Semi-littoral 



Sublittoral 



5 



30 



39 



14 



31 



22 



33 



15 



3 



6 







58 



76 



64 



From a comparison of the number of species of the sublittoral 

 zone with that of the littoral and semi-littoral zones it is seen that 

 it is smallest in the littoral zone, somewhat larger in the sublittoral 

 zone and considerably larger in the semi-littoral zone. Species of 

 green algae occur most abundantly in the littoral zone, and their 

 number is infinitesimal in the sublittoral zone. Red algae are most 

 numerous in the sublittoral zone and very scarce in the littoral 

 zone. The brown algae are more evenly distributed in the different 

 zones, yet they are richest in species in the semi-littoral zone. The 

 blue-green algae are found exclusively in the littoral zone. 



In the semi-littoral zone the large brown alga? do not occur in 

 masses like, for example, the belt of Facus in the upper littoral 



1 As regards the majority' of the species (see Table 7) it is easj' to decide 

 whether they are littoral, semi-littoral or sublittoral, but there are some species, 

 nevertheless, which it is difficult to refer definitelj' to any one of the three zones 

 mentioned, and therefore it is sometimes a matter of opinion whether they should 

 be reckoned in the one or the other. By perusing the table these species are 

 easily detected. 



2 Two species, Delesseria Baerii and Bonnemaisonia asparagoides are not in- 

 cluded as their habitat is unknown to me (see 31, pp. 140, 141). 



