The morphology of naphthalene and anthracene
crystals has been studied both theoretically and experimentally. A connected
net analysis shows that the faces {011} and {2-1-1} contain a pair of symmetry-related
connected nets giving rise to a new phenomenon called symmetry roughening.
Experimentally the {011} and {2-1-1} faces have only been observed on naphthalene
crystals grown from the vapor at very low driving forces. Upon increasing
the driving force, the {011} faces grow out very rapidly as flat faces
at very low supersaturation, For anthracene these faces have never been
observed. In this paper the relation between the connected net structure
of crystal faces and the experimentally observed growth behavior is discussed.