A calcium oxalate-secreting tissue in branchlets of the Casuarinaceae

Summary Deciduous branchlets of casuarina trees have an unusual calcium oxalate-secreting system in which the epidermal tissue deposits calcium oxalate crystals in cell walls of the branchlet surface. These prismatic crystals were identified by light and electron microscopy, histochemistry, and elemental X-ray analysis. This calcium oxalate-secreting tissue was found in all species of casuarinas examined, including three of the four genera of the Casuarinaceae:Allocasuarina sp.,Casuarina sp., andGymnostoma papuanum. Because crystals were present throughout the epidermis soon after it formed, the mechanism for their induction was likely to be different than that for calcium oxalate crystal idioblasts. Secreting cells had a complex endoplasmic reticulum that may be involved in the secretory process.Abbreviations EDS energy-dispersive X-ray spectroscopy - HPF/FS high pressure-frozen/freeze-substituted - SEM scanning electron microscopy - TEM transmission electron microscopy Dedicated to the memory of Professor John G. Torrey