Clare Island Survey— Marine Algae.. 15 129 



them being rolled up as if by the action of the waves, and in that state apparently 

 continued to grow, and throwing out from the root, which was in the centre, a 

 prodigious number of shoots in all directions, so as to give the thick and bushy 

 appearance above described." 



There can be no doubt that the present plant is merely a variety of 

 A. nodosum, and is comparable to the peculiar detached forms of Fucus and 

 Pelvetia which occur in other localities. (See Baker, '12, p. 283, and Oliver in 

 Tansley, '11, p. 364.) Whether it originates in the manner described below 

 for var. scorpioides I was unable to decide, but it appears highly probable. No 

 intermediates between the detached form and the normal A. nodosum were 

 found, but there was an evident link with var. scorpioides, and certain specimens 

 were difficult to place. It is possible that the variety Mackaii arises only at 

 certain seasons of the year, in which case a prolonged stay in the locality 

 might be necessary in order to discover its origin. 



The plants lie as loose densely branched tufts (up to a square yard in area) 

 on the flat sandy mud between patches of rock, and when the tide returns 

 they do not float, but become perfectly submerged. They appear to be seldom 

 disturbed by wave-action. Air-bladders are numerous, but very small. A 

 few tufts of Polysiphonia fastigiata were noted on some specimens, and also 

 on -var. scorpioides ; but on the whole this epiphyte was absent. Many quiet 

 land-locked areas exist in Aehill Sound and Bellaeragher Bay ; but no 

 examples of var. Mackaii were found, so that the Boundstone locality still 

 remains the only positive station in Ireland for the plant. 1 



Although C. Agardh, as early as 1824, reduced Fucus Mackaii to a variety 

 of F. nodosus, no one appears to have used the combination employed in the 

 present report. Of late years there has been a tendency to follow Harvey, 

 who regarded it as a distinct species. Holmes and Batters ('90) removed the 

 plant to Ascophyllum ; and their name, A. Mackaii, has since come into 

 general use. 



Var. scorpioides Hauck. — A few plants of this curious variety occurred in 

 some muddy areas in the inner part of Boundstone Bay intermixed with var. 

 Mackaii. They were more or less imbedded in the mud, and formed much 

 smaller tufts than the latter. Beinke's explanation as to the origin of this 

 form in the brackish waters of the Baltic Sea is as follows : — Isolated floating 

 pieces of A. nodosum are washed in by currents from the more open Skagerack, 

 and come to rest in the quiet creeks, where they put forth numerous small 

 adventitious branches from the marginal cryptostomata of the thallus. 



1 Miss Knowles kindly informs me that specimens labelled A. Mackaii, collected in Lame and 

 Belfast Loughs by D. Moore and J. Doran respectively, exist in the Dublin Museum. There is, 

 however, some uncertainty as to both specimens, and though the districts have been fairly carefully 

 worked, other observers have not noted the plant. 



R.I.A. PROC, VOL. XXXI. R 15 



