The Latin name for a species of kelp, also known as brown seaweed. Applied topically, it helps soothe and, like all forms of seaweed, has some amount of moisture-binding properties.
References for this information:
Journal of the European Academy of Dermatology and Venereology, September 2007, pages 1,124-1,125
Biomedical Chromotography, April 2004, pages 183-190