Calcium Oxalate Crystals in Monocotyledons: A Review of their Structure and Systematics

Three main types of calcium oxalate crystal occur in monocotyledons:raphides, styloids and druses, although intermediates are sometimesrecorded. The presence or absence of the different crystal typesmay represent ‘useful’ taxonomic characters. Forinstance, styloids are characteristic of some families of Asparagales,notably Iridaceae, where raphides are entirely absent. The presenceof styloids is therefore a synapomorphy for some families (e.g.Iridaceae) or groups of families (e.g. Philydraceae, Pontederiaceaeand Haemodoraceae). This paper reviews and presents new dataon the occurrence of these crystal types, with respect to currentsystematic investigations on the monocotyledons. Copyright 1999Annals of Botany Company Calcium oxalate, crystals, raphides, styloids, druses, monocotyledons, systematics, development.