Wood and stem anatomy of Stegnosperma (Caryophyllales); phylogenetic relationships; nature of lateral meristems and successive cambial activity

Wood and bark histology data on stems of two species of Stegnosperma (Stegnospermataceae, or Phytolaccaceae s.l.) is presented, complementing previous accounts. Wood of Stegnosperma is relatively primitive within Caryophyllales because of presence of tracheids, diffuse parenchyma, and both multiseriate and uniseriate rays. The solitary nature of vessels is held to be correlated with tracheid presence, as in other groups of dicotyledons with vessels solitary or nearly so. Bark anatomy is newly reported for the genus. The method of section used permits analysis of divisions in cells with primary walls. Radial rows of parenchyma ('secondary cortex') develop in the inner cortex and an perpetuated by tangential divisions collectively termed a diffuse lateral meristem here. Successive cambia form within the radial rows of parenchyma. Despite diverse terminology and interpretations in literature on plants with successive cambia, the successive cambia and their origin in Stegnosperma are believed to represent the same anatomical phenomena as in other Phytolaccaceae s.l.