Leaf anatomy of Cunoniaceae

Abstract

A study of leaf anatomy of 24 genera of Cunoniaceae was made. The prevailing petiole vasculature is a nearly complete, usually adaxially flattened, medullated cylinder with the flat dorsal segment separated from the ventral arc. Medullary and cortical vasculation in Codia, Cunonia, Geissois and Pancheria is correlated with an increase in leaf coriaceousness. Very few characters are uniformly found in leaves of all species; these are druse or prismatic crystals, bifacial mesophyll and unicellular and simple trichomes. In most species vein sheathing occurs. Characters of the lamina that show variation and are useful in generic delimitation are: trichome type, presence of a hypodermis, occurrence of mucilaginous cells, presence of specialized terminal veinlet cells, major and higher order venation patterns, vein sheathing type, and mature stomatal types. Stomata are of the anomocytic, paracytic or anisocytic types. Leaves of various cunoniaceous species of xerophytic environments exhibit a leathery texture, thicker cuticle, more intensive sclerification along the veins, a sclerified hypodermis, and an increase in the amount of vascular tissue per unit area. Leaf anatomy does not provide immediate clues toward elucidating the relationships of cunoniaceous genera.