New observations regarding secondary growth and vascular tissues in Welwitschia are based on roots (used because of the longitudinal orientation of most vascular tissues). Welwitschia has successive cambia that produce xylem and phloem. Contrary to previous reports, the cambia produce secondary phloem with phloem rays and secondary xylem that has readily definable xylem rays and axial parenchyma. Internal sculpturing (grooves associated with pit apertures) of tracheary elements is figured with SEM; observations confirm the descriptions of Bierhorst (1960). Tori and vesturing are apparently absent on pits of tracheary elements. Abundance of gelatinous secondary walls may be related to water economy to a minor extent. A feature recently reported for Ephedra wood is newly reported for xylem rays, phloem rays and conjunctive tissue of Welwitschia: presence of minute calcium oxalate crystals lining intercellular spaces. This feature is apparently limited to the two genera. The ontogenetic origin of vascular strands added by secondary activity can be traced to phelloderm. In this feature, Welwitschia differs from Gnetum, in which the ultimate origin of new cambia can be traced to cortical tissues. Keywords: cambial variants, Ephedra, Gnetum, successive cambia, wood histology.