Nostoc \Nos"toc\, prop. n. [F.] (Bot.)
A genus of algae. The plants are composed of moniliform cells
imbedded in a gelatinous substance.
[1913 Webster]
Note: {Nostoc commune} is found on the ground, and is
ordinarily not seen; but after a rain it swells up into
a conspicuous jellylike mass, which was formerly
supposed to have fallen from the sky, whence the
popular names, {fallen star} and {star jelly}. Also
called {witches' butter}.
[1913 Webster]