CULTURE AND HYBRIDIZATION STUDIES ON PETROCELIS (RHODOPHYTA) FROM ALASKA AND CALIFORNIA1,2

Cultured tetraspores of Petrocelis middendorffii (Ruprecht) Kjellman from Amchitka Island, Alaska, gave rise to foliose, dioecious gametophytes similar to cultured gametophytes of P. franciscana Setchell & Gardner. A 1:1 ratio male:female gametophytes was obtained. Fertilized female plants produced cystocarps and carpospores that gave rise to crustose plants anatomically similar to field-collected Petro-celis sporophytes. Cultured male gametophytes of P. middendorffii were interfertile with cultured female blades of field-collected Gigartina pacifica Kjellman. Cultured P. middendorffii gametophytes from Amchitka were interfertile with cultured gametophytes of P. franciscana from 2 localities in California. Hybrid carpospores gave rise to crustose sporophytes that have not reproduced. Anatomical comparisons of P. middendorffii from Amchitka with P. franciscana from California showed no important differences in the characters originally used to separate these species. The interfertility of cultured Petrocelis gametophytes from california and Amchitka as well as the similarities of the history and anatomy suggests that a single species is involved. P. franciscana is reduced to a synonym of P. middendorfii.