15 50 Proceeding* of the Royal Irish Academy. 



The Swedish vegetation described by Kylin is very different. Alaria is 

 absent, and the vertical rocks are clothed with L. digitata and L. saccharina 

 var. bullata. In the most open spots L. digitata vex. cuneata is dominant. 

 The L. Cloustoni vegetation is entirely separate from L. digitata, being found 

 only in the deeper part of the sub-littoral region, appearing first in about 

 15 m. of water. Boye's account of the Norwegian flora (according to 

 Borgesen's summary) agrees with that of the Faeroes ; and Kylin's notes on 

 the vegetation near Bergen ('10) indicate the preponderance of Alaria and 

 L. Cloustoni. The Iceland vegetation resembles that of the Faeroes, but is 

 enriched by the presence of L. nigripes and Saccorhiza dermatodea. In the 

 south of England Alaria is rare except in Cornwall, but apart from its 

 absence the Clare Island vegetation agrees well with that noted in Dorset. 

 The exposed rocky coasts of Ireland are, however, more favourable for an 

 extensive Laminaria vegetation, and are highly suitable for a growth of 

 Alaria. 



Encrusting Alga Vegetation (sub-littoral). 



The Lithothamnium vegetation of the littoral region extends downwards 

 into the deepest parts of the sub-littoral, but, owing to the difficulty of dredging 

 amongst a dense growth of Laminaria digitata and L. Cloustoni, it is difficult 

 to ascertain the amount of growth and the relative abundance of the species. 

 An extensive coating of calcareous algae is, however, present, and on exposed 

 coasts probably occupies a large part of the available rock-surface, though soft 

 encrusting species, such as Cruoria pellita, Cruoriella, and Peyssonnelia, occur 

 with it. Lithophyllum incrustans enters the sub-littoral ; but, as far as could be 

 seen, the Lithothamnium 'band at the lowest tide-level consists mainly of 

 L. poly morphum, and this extends downwards for several fathoms. Other 

 species dredged were L. laevigatum and L. compactum. The fruticulose 

 calcareous algae, such as L. calcareum and L. fasciculatum, are characteristic 

 of sheltered shores (p. 69). 



B. — Sheltered Coast Scries. 



(a) Littoral region. 



Several of the associations found on sheltered coasts have been already 

 dealt with. In some cases the principal differences noticeable in passing from 

 the open shores to quieter conditions have been pointed out, so that re-descrip- 

 tion is unnecessary. In other cases, though the associations have been described, 

 their growth in sheltered localities requires special notice ; yet other 

 communities are peculiar to such regions. 



