Pit membrane remnants in perforation plates and other vessel details of Cornales

Perforation plates and other vessel details as studied with scanning electron microscopy (SEM) have been reported for four species of Cornaceae (s.l.): similar features are shown by the four, suggesting that a more extensive sampling of the family might reveal similar phenomena. Perforation plates contain pit membrane remnants in the form of threads or, less commonly, laminar portions perforated by pores. When least well-represented, the pit membrane remnants are restricted to lateral ends of perforations and to the perforations transitional to lateral wall pitting. Perforations are all clearly bordered. Helical thickenings that do not form a continuous gyre are reported for the vessel walls of Aucuba. The presence of pit membrane remnants in vessel elements of Cornaceae correlates with the mesic habitats occupied by species in this family. The presence and type of pit membrane remnants reported by us in the three genera is very similar, although pit membrane remnants are doubtless a symplesiomorphy and thus not an indicator of relationships. The presence of pit membrane remnants in the three genera, however, does attest to the primitiveness of wood and other features of Cornaceae s.l.