15 48 Proceedings of the Royal Irish Academy. 



Laminaria Association. 



Clare Island is girdled at low-water mark with a fine belt of Laminaria, 

 which descends on all sides deep down into the snb-littoral region. With the 

 exception of the somewhat doubtful L. hieroglyphica, all the English species 

 occur, so that the west of Ireland presents the exposed Laminaria vegetation 

 of the British Isles in its most varied form. Though a submerged association, 

 each species reaches to the top of the sub-littoral region, and is thus visible 

 during the lowest spring-tides. Alaria and L. digitata are uppermost, and 

 are often uncovered ; Saccorhiza and L. saccharina follow, and usually show 

 in calm weather, whilst the erect stipes of L. Cloustoni protrude in favoured 

 localities only. Alaria, L. digitata, and L. Cloustoni form well-marked belts 

 which are always to be found on the type of shore that they respectively 

 require, whereas the growth of Saccorhiza, and L. saccharina, though at 

 times plentiful, is scattered and local. 



A steep coast with almost perpendicular rocks is the Alaria shore par excellence, 

 though L. digitata is also usually present. On sloping rocks the same 

 vegetation obtains, the amount of L. digitata increasing as the shore becomes 

 less steep, till at length Alaria disappears altogether. L. digitata, often 

 descends into many fathoms (at least 8) ; but Alaria appears to form a shallow 

 belt in the uppermost part of the littoral region. L. Cloustoni enjoys the 

 Atlantic swell, but prefers a Hat bottom, and is absent on steep rocks. 

 "Within the shelter of a reef, or in other similarly protected spots, the plants 

 are found nearer the surface of the water, and at the lowest tides the tops of 

 their stipes protrude. In such positions the association may be conveniently 

 examined from a boat (e.g., at Eoonah Quay). 



A flat or gently sloping bottom with a certain amount of shelter is most 

 suitable for Saccorhiza and L. ■saccharina. In certain spots on the south shore, 

 and especially in channels between the rocks, the former grows in plot-like 

 areas, which may be easily examined from the rocks in quiet weather. It is 

 also plentful in the shallow water off Kimiacorra. Streak-like patches of 

 L. saccharina have also been noted in these localities, but the plant is more 

 characteristic of quiet regions. 



As stated on p. 15, the Laminaria association, though it may be partially 

 uncovered during spring-tides, marks in reality the upper limit of the sub- 

 littoral region. The amount uncovered varies with the exposure. In the 

 most boisterous spots Alaria ascends high, and consequently, if a spell of 

 quiet weather synchronizes with spring-tides, a considerable amount, 3-5 feet, 

 is left bare. Borgesen mentions a case in the Faeroes, where Alaria flourished 

 at a level above that of high-water line. Nothing like this has been seen in 



