This study of the brown algal genus Laminaria Lamour consisted of (1) a critical review of the taxonomy and distribution of taxa of Laminaria occurring in the northeast Pacific, (2) a description of the life histories and growth patterns of long and short stipe forms of L. groenlandica and L. saccharina, (3) an evaluation of the roles of temperature, salinity, and water motion as possible determinants of local distributions of long and short stipe forms of L. groenlandica and L. saccharina, and (4) an evaluation of the roles of temperature, salinity, exposure, and submarine illumination in determining the vertical distribution of L. saccharina. These studies were made from 1961 to 1965. Ten species of Laminaria are recognized for the northeast Pacific: L. groenlandica Rosenv.; L. farlowii Setchell; L. saccharina (L.) Lamour.; L. setchellii Silva; L. dentigera Kjellman; L. longlpes Bory; L. sinclairii (Harvey ex Hooker f. et Harvey) Farlow, Anderson et_ Eaton; L. ephemera Setchell; L. yezoensis Miyabe; and L. complanata (Setchell et Gardner) Setchell. Laminaria cordata Dawson is considered conspecific with L. saccharina, L. personata Setchell and Gardner is regarded conspecific with L. yezoensis, and L. platymeris De la Pyl. (sensu Setchell and Gardner) is considered conspecific with L. groenlandica. Pour forms of L. groenlandica are recognized for the northeast Pacific. These forms are not considered as legitimate taxonomic entities but are distinguished merely to provide a means of facilitating discussion. The known habitat requirements for all ten species were broadened and the known distributions of all species, excepting L. groenlandica, were extended. Laminaria saccharina and L. groenlandica produced sori in the late spring and winter. New sporophytes of L. groenlandica appeared throughout the year, whereas those of L. saccharina appeared in late winter and early fall. Depending upon culture conditions, two morphologically distinct forms of gametophytes were produced by both species: large gametophytes were produced in conditions of high temperature and low salinity; and small gametophytes in conditions of low temperature and high salinity. Abnormal sporophytes were observed under conditions conducive to formation of large gametophytes. Patterns of growth for the blades of the two species were essentially the same.. The growth rate decreased with increase in distance from the blade base, and the position of greatest longitudinal growth coincided with the position of greatest lateral growth. The distributions of L. saccharina and the two forms of L. groenlandica about Vancouver Island were correlated with temperature, salinity, and water motion. The two forms of L. groenlandica were absent from areas of high temperature and low salinity; L. saccharina was absent from areas subjected to surf. These field conclusions were subjected to laboratory and field tests involving gametophytes and sporophytes of both species. The distributions of the two forms of L. groenlandica can be explained on the basis of temperature and salinity distributions. Both forms require low temperature and high salinity for survival. Laminaria saccharina has a wide range of tolerance to temperature and salinity. Surf appears to be the agent controlling the distribution of this species. The upper limits of L. saccharina, as observed in Burrard Inlet, are thought to-be directly related, to air temperature and insolation and indirectly related to tidal characteristics. The lower limits appear to reflect the compensation depth of this species. / Science, Faculty of / Botany, Department of / Graduate