Morphology of Adult Leaves in the Cyclanthaceae (Monocotyledoneae)

Abstract

Cyclanthaceous adult leaves consist of lamina, sheath, frequently petiole, and sometimes a transition zone between petiole and lamina. Sheath margins may terminate in auricles or stipules; occasionally, a hastula or hastula-like structure develops at the base of the lamina. Laminae are undivided (Ludovia spp.) or divided (all other taxa studied). Each lamina exhibits tissue pad(s) (except in Ludovia spp.), one or three costae, and, in the Carludovicoideae, adaxial and abaxial folds. Tricostate leaves develop in Cyclanthus and either consistently or intermittently in five genera of Carludovicoideae. The number of abaxial folds per lamina varies from two (Sphaeradenia crocea) to 52 (Carludovica palmata). In carludovicoid laminae, major veins and cell files of the epidermis and mesophyll extend parallel to folds, and where present, ridges do so. Folds, ridges, major veins, and cell files are oriented differently in laminae of Ludovia spp. from those of other carludovicoid taxa studied, and, in the nonplicate laminae of Cyclanthus, major veins and cell files are arranged like those in laminae of Carludovicoideae other than Ludovia. These differences in arrangement help explain why undivided and divided laminae develop in Ludovia and all other taxa, respectively. Cyclanthaceous laminae become divided because of tearing of tissue, and in Carludovicoideae other than Ludovia, tearing permits expanding laminae to become more planar. The phylogeny of the Cyclanthaceae and the degree of their relationship to the Palmae are discussed.