DISTRIBUTION OF CERTAIN BRITISH ALG^ 37 



effect of this on the vegetation is very apparent. During westerly 

 gales and high seas the gravel is dashed over rocks ; and even such 

 tough plants as Ascopliijllum are in places shorn off, while the 

 scarcity of many of the more delicate species in pools which 

 appear otherwise suitable, is no doubt to be attributed to the 

 same cause. Through the kindness of Professor R. H. Yapp I 

 was able to look through the algal herbarium at the University 

 College, but though possessing a good variety of species for the 

 type of shore, none of the algae in question were represented. 

 Professor Yapp informed me that similar ground continues as far 

 south as Aberaeron, and that the same type of vegetation obtains: 

 the presence of loose stones and sand would doubtless be specially 

 inimical to Godium mucronatum, and he did not recollect having 

 seen any representatives of the genus in the neighbourhood. The 

 same factor is probably also operative on the flat rocky shore 

 south of Barmouth, though it was not so clearly demonstrated. 

 At Borth the ground is obviously unsuitable. 



As far as Cardigan Bay is concerned, therefore, we may be 

 fairly safe in saying that over a very large area (probably from 

 Portmadoc to Aberaeron) the three species under consideration 

 are absent, though as shown above this may be largely accounted 

 for by unsuitable conditions. 



2. Pembrokeshire (August 18th-21st). — Pembrokeshire ap- 

 peared likely to prove interesting, not only from its rocks being 

 of a different character to those of Cardigan Bay, but from its 

 position at the extreme south-west corner of Wales. It was 

 possible that the rock-loving species in question might obtain a 

 footing in that neighbourhood, and that they might descend as 

 far south as St. David's Head, though they were not known to 

 occur on the coasts of Cornwall, the other side of the British 

 Channel. Fishguard was chosen as a centre ; it is easy of access, 

 and, unlike Tenby and Milford, open to the west. But in this 

 neighbourhood the precipitous cliffs are a great obstacle ; and the 

 time lost in going from one bit of accessible ground to another, 

 when tides waiting for no man are in question, is a serious 

 matter. 



In a southerly direction the coast-line was examined at 

 irregular intervals from Fishguard to a point about half-way 

 between Strumble Head and St. David's. The cliffs and head- 

 lands are for the most part composed of volcanic rocks, and these 

 descend sheer into the sea ; but bays of slaty rocks, which are 

 more accessible, are also present. The latter are strewn below 

 with stones and gravel, and, as can be seen from above, they 

 support little or no vegetation. Two near Pembrush Point 

 were descended by paths none too safe, but practically no algal 

 growth, save Enteromorpha and a small amount of Fucus, was 

 found. Time did not permit of extending the search to the 

 Head itself, but it is probable that the same type of coast 

 continues. It is very unsuitable for littoral algae owing to the 

 steep cliffs and lack of reefs. 



North of Fishguard a much better vegetation was met with. 



