The basic pollen wall types in Araceae

An ultrastructural investigation of 60 species, representing 47 genera, of Araceae showed two basic pollen wall types, each with two subtypes. The two main types are distinguished by presence (type 1) or absence (type 2) of an acetolysis-resistant ektexine. The subtypes are differentiated by a structured (type 1a) or unstructured (type 1b) ektexine, respectively, and the presence (type 2a) or absence (type 2b) of polysaccharidic wall ornamentations. A characteristic of all types is a spongy endexine, which is electron dense after thiocarbohydrazide-silver proteinate staining and is only partially resistant to acetolysis.