The Collaborative International Dictionary of English v.0.48:

sloakan \sloak"an\ (sl[=o]k"an), n. (Bot.)
   A species of seaweed. See 3d Laver. [Spelled also
   slowcawn.]
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Laver \La"ver\ (l[=a]"v[~e]r), n.
   The fronds of certain marine alg[ae] used as food, and for
   making a sauce called laver sauce. Green laver is the Ulva
   latissima; purple laver, Porphyra laciniata and Porphyra
   vulgaris. It is prepared by stewing, either alone or with
   other vegetables, and with various condiments; -- called also
   sloke, or sloakan.
   [1913 Webster]

   Mountain laver (Bot.), a reddish gelatinous alga of the
      genus Palmella, found on the sides of mountains
      [1913 Webster]