(1):

(n.) A sweet white efflorescence from dried fronds of kelp, especially from those of the Laminaria saccharina, or devil's apron.

(2):

(n.) A white crystalline substance of a sweet taste obtained from a so-called manna, the dried sap of the flowering ash (Fraxinus ornus); - called also mannitol, and hydroxy hexane. Cf. Dulcite.