4 J. H. PRICE, I. TITTLEY & W. D. RICHARDSON 



Most of the known British and continental localities are sheltered from the direct effects of 

 south-westerly and westerly seas (there are exceptions in the Channel Islands, Atlantic southern 

 France and, apparently, in Portugal); in many cases, they are in very sheltered bays. In the 

 Mediterranean, Padina usually grows in detritus over flat or shallowly inclined surfaces, although 

 (Ramon, pers. comm.) it is found directly attached on rock surfaces along the coasts of Israel. In 

 Britain, P. pavonica is most frequently found on rocks covered by soft sediments, in which the 

 basal portions of the plants are buried; these probably have some anchoring effect on the other- 

 wise mobile detritus. Feldmann (1938) came to a similar conclusion regarding plants of the 

 Banyuls area and it is true also for elsewhere in the distribution range. Plants have not been 

 detected in Britain growing directly attached to hard rock surfaces. In many of the areas in which 

 Padina occurs, softer rocks present have been eroded by wave-action, frost, and other agencies, but 

 any ledges of harder rocks have more strongly resisted erosion. Where these harder ledges have a 

 gentle slope, sediment has been deposited. Padina appears able easily to exploit this type of surface, 

 on which few other macrobenthic algae seem to grow successfully. In pools, plants of Padina grow 

 on similar substrata and may there be associated with a variety of small lower-shore algae. 

 Norris (1972, unpublished)* observed certain areas of Bembridge Lagoon, Isle of Wight, where in 

 small valleys of eroded softer substrata between more solid raised areas of mudstone there was 

 generally patchwork absence (valleys) and presence (raised areas) of Padina. He therefore suggested 

 that P. pavonica '. . . cannot easily cope with a shifting substratum'. Some degree of compaction of 

 detritus does seem to be necessary for effective colonisation by Padina; early growth stages and 

 embryo populations apparently tend to be susceptible to substrate movement. The compaction 

 may derive, in the right circumstances, from the anchoring effect of Padina itself. 



The flabellate fronds of Padina pavonica commonly die back en masse during the winter months 

 in Britain, unlike many parts of the Mediterranean, where plants in good growth can be observed 

 during most months of the year in all but the really shallowest of infralittoral populations, 

 although die-back occurs in individual plants. Even in southern England, however, it is possible 

 during milder winters to observe the reduced fronds throughout the whole of the adverse weather 

 period. The total disappearance in more usual winter conditions is only apparent, being the result 

 of a more drastic die-back to leave only consistently buried portions that perennate. If the exact 

 position of a population is known, rhizomatous portions of P. pavonica may be readily detected 

 during the winter in scrapings of sediment from the summer-growth location. Winter collecting in 

 previous eras was certainly rare, but aside from that it is not entirely surprising that, previous to 

 1968, few authentic instances existed of recordings from British shores during the winter months. 

 The only traced examples are the 1908-09 winter data from Weymouth, in Cotton's field notes 

 (BM). The more usual pattern is exemplified by Norris (1972, unpublished), who indicated that 

 he first detected growth at Bembridge, Isle of Wight, at the end of May, although plants may have 

 been visible at an earlier date since observations were only commenced at this time. The Bembridge 

 populations almost died back by the second week in October although, possibly due to lack of 

 wave-action and a slightly higher temperature, plants growing in the laboratory persisted until the 

 end of November. This accords with our field observations of persistent visible growth throughout 

 milder winter periods, and with Cotton's earlier statements. 



Life-history 



Reproductive patterns, and perhaps therefore life-history in the field, appear to be incomplete or 

 only very rarely complete on British shores. This seems to apply equally to the largest part of 

 Padina pavonica distribution elsewhere. Norris (1972, unpublished) did not record gametangial 

 plants from Bembridge, Lyme Regis, or Ladram Bay, although the former two yielded tetrasporic 

 material. Williams (1905) stated, without further explanation, that during summers 1904 and 1905 

 he had detected '. . . but very few . . .' sexual plants of Padina in Dorset (Weymouth) and Devon 

 (Torquay; Sidmouth). Carter (1927) detected only tetrasporic plants in P. pavonica at Ladram Bay, 

 Chapman's Pool, Lulworth Cove and Nothe Rocks, Weymouth, but noted meiotic division, which 



* We are indebted to W. F. Farnham, Portsmouth Polytechnic, for drawing our attention to this work. 



