MORPHOLOGICAL VARIATION IN PTEROCLADIA PYRAMIDALE(1).

Seven Pacific species of Pterocladia and European collections of P. capillacea were examined. Ten morphological criteria were assessed in specimens of P. pyramiclale from 10 intertidal and subtidal populations in San Diego, California. The observations obtained from these populations were compared with descriptions and specimens of P. complanata from southern and Baja California; P. mexicana, P. robusta, P. okamurai, and P. okamurai f. densa from the Galapagos Islands and Baja California; and P. tenuis and P. densa from Japan. All these taxa were found conspecific with P. pyramidale. Pterocladia capillacea from Europe, using the same characters, was not distinct from the Pacific assemblage. These two taxa should be united under the name of Pterocladia capillacea (Gmelin) Bornet & Thuret (1876). Pterocladia capillacea (= P. pyramidale) grows under varied conditions and exhibits various growth forms accordingly, in southern California. Variation between several forms seems related to the degree of exposure to light, temperature, and surf action; such forms are recognizable in herbarium collections from other parts of the world. Abundant fertile material occurs in southern California.