Clare Island Survey — Marine Algae. 16 5a 



marked difference in the vegetation as long as Ascophylium remains. A 

 slight exposure, however, is sufficient to affect this species, and with its 

 disappearance the association is robbed of one of its most conspicuous elements. 

 Ascophylium begins to disappear on the outer sides of the islands, but 

 persists in all cases on the inner sides. West of the islands it is only found 

 in certain places, though this perhaps is largely due to the lack of good 

 mooring. But, in spite of this, there is no question whatever that in the 

 Survey-area Ascophylium is far more susceptible to exposure than F.vesiculoms. 

 This is in agreement with observations in other parts of the British Isles, and 

 also with accounts that have been given of the Norway Fucus- vegetation 

 (Boye, '94, and Kylin, '10). The conditions described for the Faeroes, 

 where Ascophylium is the less susceptible of the two, are very remarkable, 

 and, as far as known, unique. The result of exposure in producing a change 

 in form in the various constituents of the association is very marked. It is 

 best seen in F. spiralis. F. vesiculosus also produces a wealth of form, but 

 the variations are more difficult to connect with external conditions. 

 Remarks on these points occur in the notes on each species given later. 



Fucus Farms. — The botanical features of the plots, planted with stones in 

 order to obtain a growth of Fucus for use as manure, may be dealt with here. 

 The farms are formed on flat stretches of sand exposed at low water. They 

 may either extend from the shore, or be laid out as isolated patches in the 

 middle of the strand. The rapid colonization, and the luxuriance of the 

 subsequent vegetation, prove beyond question the effect of anchorage. 



The stones are covered mostly by F. vesiculosus, though a small amount of 

 Ascophylium sometimes occurs. At the lowest levels there are occasionally 

 encircling belts of F. serratus, but the stones are not as a rule placed 

 sufficiently low for this species. F. vesiculosus is very luxuriant, forming large 

 tufts, bright yellow in summer and deep green in winter, with numerous 

 bladders and abundant fruit. F. serratus, when present, grows equally 

 vigorously, with fine broad fronds often a yard in length. The plants are 

 cut in February after two full years' growth, and the stones turned over for 

 a new crop of sporelings to develop. 



It is somewhat remarkable that this artificially produced vegetation con- 

 sists of a practically pure association of F. vesiculosa, forming thus a striking 

 contrast to vegetation obtaining on mud-flats (e.g., Belfast Lough, South- 

 ampton Water). The latter are colonized by mussels, and these support a 

 pure growth of Ulv a Lactuca, Ulva, and many other adaptable algae, are 

 present in Clew Bay, but Fucus has complete sway on the stone plots. Tr 

 would be interesting to know whether Fucus would develop if stones of 

 sufficiently large size could be maintained on the mud-flats of Belfast Lough. 



