macrocystis

from The Collaborative International Dictionary of English v.0.48

Macrocystis \Mac`ro*cys"tis\, n. [NL. See {Macro-}, and {Cyst}.]
   (Bot.)
   An immensely long blackish seaweed of the Pacific
   ({Macrocystis pyrifera}), having numerous almond-shaped air
   vessels.
   [1913 Webster]