Wood anatomy, stem anatomy, and cambial activity of Barbeuia (Caryophyllales)

Liquid-preserved material of mature stems of Barbeuia madagascnriensis Steud. permitted analysis of meristematic activities. The species has successive cambia, each producing secondary xylem and phloem; outside of these vascular strands is a nondiffuse lateral meristem, probably functionally a single cell in thickness, which produces radial files of secondary cortex to the outside and conjunctive tissue and vascular cambia to the inside. The secondary xylem of Barbeuia has dimorphism in vessel diameter, reminiscent of vessel dimorphism in other lianas, such as Agdestis. Diffuse parenchyma and tracheids, found in Barbeuia, also occur in Stegnosperma and Agdestis but not other Phytolaccaceae s.l., and are traditionally considered primitive features. Wood anatomy and lateral meristem activity of Barbeuia are distinctive enough to support segregation of the genus from Phytolaccaceae s.s.