IT is generally believed that the fast and unidirectional growth of the major part of whiskers may be partly due to the winding up of one or more screw dislocations along the whisker axis1. S. Amelinckx demonstrated this dislocation mechanism in sodium chloride whiskers by the decoration technique2. He observed on whiskers grown by a simple method also the broadening of hollow, tube-like pyramids probably developed from spiral terraces which are thought to originate from axial screw dislocations3.