MARINE ALGAL VEGETATION 89 



close to this limit; 6 species (1 red, 3 brown, 2 green) have their 

 area of distribution in the upper and lower littoral zones, and to 

 a depth of 10 metres, these species are mentioned under the Upper 

 Littoral Zone, and there, 5 of them are reckoned as littoral. 35 

 species (10 red, 15 brown, 10 green) grow in the lower littoral 

 zone, and to a depth of about 10 metres. They appear to be about 

 as common in the lower littoral zone as in the belt between the 

 limit of low-tide and the depth mentioned. 18 species (12 red, 3 

 brown, 3 green) grow in the lower littoral zone, and to a depth 

 of more than 10 metres; these belong to the species which have a 

 lower downward range, 15 of them have their uppermost limit in 

 the lower littoral zone, and 3 of them in the upper littoral zone. 



The species characteristic of the lower littoral zone are especially 

 the 19 species which are found there only, and the 35 species 

 which extend to a depth of about 10 metres, for some of these (e. g. 

 Rhodymenia and Halosaccion) , by occurring in masses, often cha- 

 racterize large portions of the lower littoral zone. 



2. The Belt down to a depth of about 10 metres. In 

 the table 103 species are recorded from this belt. Of these, two 

 occur also in the upper littoral zone, and have been previously 

 mentioned (Rhodochorton Rothii and Hildenbrandia) , 6 occur also 

 in the upper and lower littoral zones and are mentioned above, 

 35 occur also in the lower littoral zone (see under this heading); 

 while 9 species are found only at this depth, but of these some 

 may be presumed to extend further downwards and some may 

 possibly occur in the lower littoral zone. 19 species extend down- 

 wards, with their uppermost limit in the upper and lower littoral 

 zones, as, for example, Conchocelis rosea which occurs in the upper 

 littoral zone and is absent from the lower littoral zone, besides the 

 18 species mentioned under the Lower Littoral Zone. 32 species 

 with a downward range have their uppermost limit at a depth of 

 about 10 metres. 



Besides the 9 species which are found only in this belt, it is 

 especially the 35 species which this belt has in common with the 

 lower littoral zone which characterize the belt, as some of them — 

 those mentioned under the Lower Littoral Zone — by occurring 

 in masses often characterize large portions of the bottom. 



By comparison it can easily be seen that the lower littoral 

 zone is much more closely related to this belt than to the upper 

 littoral zone, which, amongst other things, is evident from the great 



