Comparative Morphology of the Glossopodia of Three North American Isoetes Ligules
One of the most distinctive features of the heterosporous lycopsids is the presence of a ligule. This enigmatic structure is currently found only in the genera Isoetes and Selaginella. It is comprised of a basal embedded glossopodium and a free distal tongue. Previous studies have demonstrated small variations in glossopodium shape in Indian species, leading to the possibility that this structure could have taxanomic use. Serial cross, paradermal, and sagittal sections of glossopodia from three different North American species, representing three different ploidy levels, were made. 3-D digital rendering of this complex organ provided comparative data for the three North America species and allowed comparisons with previous published descriptions. In general, the overall shape of the glossopodium is similar in all three North American species. There are several structural differences among them, such as the shape of the cornuae, the length of the medimoles, and the angle of the glossopodium in comparison to the leaf axis.
School Location:USA - Ohio
Source Type:Master's Thesis
Keywords:isoetes ligule glossopodium lycophyta isoetales morphology 3 d imaging
Date of Publication:01/01/2004