Mature thalli of Fucus distichus, F. edentatus, F. serratus, and F. vesiculosus were obtained in unialgal culture from zygotes and were grown in an enriched seawater medium. The two former species were maintained in culture for more than 2 years, in which time the length of thalli of F. edentatus never exceeded 4 cm. The other species grew reasonably well with a maximum rate of elongation of about 1 cm per month for F. serratus. In all species the rates of growth were less than that observed in nature. Fertile receptacles with viable gametes were formed in F. distichus, but the other species never attained reproductive maturity. All specimens retained their characteristic morphology under identical conditions of culture, and it is suggested that morphological variation amongst Fucus spp. is due mainly to hybridization rather than to environmental conditions. There was no indication that any of these species required intertidal conditions, and no unique nutritional requirements were identified.