The Collaborative International Dictionary of English v.0.48:

Nereocystis \Ne`re*o*cys"tis\, prop. n. [NL. See Nereid, and
   Cyst.] (Bot.)
   A genus of gigantic seaweeds.
   [1913 Webster]

   Note: Nereocystis Lutkeana, of the North Pacific, has a
         stem many fathoms long, terminating in a great vesicle,
         which is crowned with a tuft of long leaves. The stem
         is used by the Alaskans for fishing lines.
         [1913 Webster]