A technique for the direct viewing of topographic images was developed based on a television system using an x-ray sensing PbO-vidicon camera tube (resolution 25 μm). Melting and growth processes of plate-shaped crystals were observed in an argon flow by this technique. The observation showed that dislocations have very high mobilities by superheating and the equilibrium dislocation density of zero is achieved just before melting. In melting of dislocation-free crystals, liquid drops (locally molten regions) were observed inside the crystals. While, crystallites appeared in the supercooled melt near the growth interface. It was found that both the drops and crystallites are not formed in 5% hydrogen/95% argon environment. Melting behavior of crystals covered with oxide films indicates that the solid-liquid interfacial free energy is greatly lowered by oxygen impurity. This oxygen effect may be responsible for both the drop and crystallite formation. Origin of swirl defects in dislocation-free crystals is discussed in the basis of these observations. Both composite and common a/2<110> dislocations were observed near the growth interface: The former are composed of three a/2<110> dislocations and are present at the interface so that, as the crystal grows, they propagate into the new crystal. They influence the interface morphology, when their Burgers vectors have the component perpendicular to the interface. The common dislocations cannot exist stably at the interface and are driven into the newly grown dislocation-free region by thermal stresses.