The relative size distributions of molecules of C-60 and higher fullerenes observed in single walled carbon nanotubes (SWNTs) produced by are vaporization of carbon in the presence of a mixed Ni/Y catalyst are described. The experimental and calculated imaging properties of the fullerenes, which were observed in ca. 5-10% of SWNTs, are also described. The in situ e-beam irradiation in a 300 kV field emission gun transmission electron microscope causes rapid coalescence of the fullerenes within the SWNTs. The incorporated fullerenes also directly impede crystal growth in SWNTs when their cavities are filled by the Liquid phase capillary method.