A COMPARISON OF PORPHYRA-DIOICA SP. NOV. AND PORPHYRA-PURPUREA (ROTH)C. AG. (RHODOPHYTA, BANGIOPHYCIDAE) IN EUROPE

This paper describes two species previously confused under the name Po rphyra purpurea (Roth) C. Ag. sensu late: Porphyra dioica sp. nov. and P. purpurea sensu stricto. The holotype (BM) of I dioica is from Sidm outh, Devon, England and the proposed neotype (BM) of P. purpurea is f rom Nord-Ost Watt, Helgoland. Porphyra dioica is characterised by havi ng olive-green to purple-brown, frequently laciniate, lanceolate to br oadly ovate fronds which fold in half when held vertically; it is dioe cious with marginal sori; spermatangial packets contain 64 spermatangi a; carposporangial packets contain 8 carpospores. Porphyra purpurea se nsu stricto is characterised by having brown to reddish-brown, usually entire, elliptical to obovate fronds; it is monoecious with male and female sori separated by a distinct line; spermatangial packets contai n 64-128 spermatangia; carposporangial packets contain 16 carpospores. Carpospores of both species develop into a filamentous ''Conchocelis' '-phase. Ecological differences are also apparent, with P. dioica occu rring in the lower midlittoral of more exposed shore regions, and P. p urpurea in the midlittoral of more sheltered locations.