A study of variation in the genus Alaria Greville

Field collections and observations of Alaria (Order Laminariales) were made throughout the intertidal zones of the temperate areas in the Northern Hemisphere. In addition a study was made of all available herbarium material. Morphology was chosen as the basis of the systematic study of the genus. The systematics of the genus were studied by a discriminant and distance function analysis, using an IBM 1620 computer. From this analysis, the characteristics of 10 species were defined. Four other species were described from herbarium material, but were not sampled in sufficient quantity for statistical analysis. The dividing lines drawn between the various species are meaningful but essentially arbitrary. Confusion in the taxonomy of the genus has two main sources. First, the taxa are not completely differentiated into distinct species. Second, differences of environment appear to play a greater role as a cause of morphological variation than do differences of genotype. The names of 107 specific and subspecific taxa of the genus Alaria, including recombinations, were discovered in an exhaustive search of the literature. Of these 107 names, 19 were eliminated as illegitimate under the rules of the International Code of Botanical Nomenclature, or were removed from the genus. The genus Pleuropterum Miyabe et Nagai was reduced to synonomy under the genus Alaria. The conservation of the generic name Alaria was re-examined and found to be adequate. A thorough search was made for possible holotypes or lectotypes of the 88 taxa remaining. Material was either shown to be the holotype or found and designated as the lectotype for 66 taxa. No relevant material could be found for 11 more of these taxa and possible material for another 11 was judged inadequate for practical systematic purposes.Science, Faculty ofBotany, Department ofGraduat