Wood Anatomy of Cercidium (Fabaceae), with Emphasis on Vessel Wall Sculpture

ABSTRAcr Quantitative and qualitative data are presented for wood anatomy of the seven species of Cercidium (including two subspecies of C. floridum as well as the hybrid C. x sonorae) currently recognized. Data on wood of Parkinsonia are presented for purposes of comparison. Vessel walls of Cercidium show unusual sculpture: coarse excrescences termed verrucae here, crateriform pits, and grooves interconnecting pit apertures. These plus crystal distribution, presence of septa in fibers, pit diameter, presence of vasicentric tracheids, and presence of diagonal vessel aggregations are probably species distinctions to various degrees. The crystal-bearing fibers of Cercidium, some of which have very thin walls, exemplify fiber dimorphism. Wood of Parkinsonia aculeata is amply distinct from that of Cercidium. Vessel element dimensions and density in Cercidium do not indicate exceptional xero-morphy for woods, perhaps because some species grow in desert washes, perhaps because other features (leaflessness, thick cuticle on stems) reduce transpiration. Vessel wall sculpture, vasicentric tracheid presence, and degree of vessel grouping are considered likely indicators of wood xeromorphy within the genus, however.