Note
Sargassum mathiesonii sp. nov. is described from a population at the mouth of the Homosassa River, Homosassa, Florida. Patterns of morphological variation were quantified as well as the plant's phenology and ontogeny. Sargassum mathiesonii is dioecious (50/50 sex ratio), produces receptacles basipetally along laterals, and has vesicle pedicels that average 1–1.7 mm in length. As judged from coefficients of variation and measurements of between-plant variation, vesicle diameter was the most stable continuous trait, followed by vesicle length, blade length: width ratio, blade width, and blade length.