Figure 2. Habit and morphology of Aureophycus aleuticus (St. George Is., 24 October 2012).

(a), erect part of sporophyte with characteristic marginal thickening at the transitional zone between blade and stipe (arrows). Arrowheads show midribs of Alaria sp., growing mixed with Aureophycus. (b), Sporophytes of different developmental stages. Arrows show flattened stipes and asterisks show basal systems (discoidal holdfast forming sorus). Note that the basal systems show unilateral development in the early stages, and the iridescent color of the basal systems including those of rather young thalli showing signs of sorus formation. (c), developed basal systems overlapping each other, with iridescent color on the surface (asterisk) showing sorus formation. [Photographs by H. Kawai].