Taxonomy of Selaginella: a study of characters, techniques, and classification in the Hong Kong species

Abstract

This study of 11 Hong Kong species of Selaginella indicates that sufficient characters exist by which they may be conveniently, consistently, and conclusively distinguished, and implies that the same is true for the rest of the genus, which suffers from chronic taxonomic confusion. Characters assessed are: leaf size, shape, epidermal cell patterns and mesophyll structure; ligule shape; patterns seen in stem transections; sporophyll shape; microsporangium shape; sporangial distribution; and spore surface ornamentation. Of these, the shape of median leaves, the maximum size of lateral leaves and epidermal cell patterns are the most significant and distinctive foliar features. These, together with spore surface ornamentation, are the most useful for distinguishing species. Correlations between the shapes of ligules, sporophylls, microsporangia, and vascular bundles indicate natural subgeneric groups. These studies suggest that there are two ways by which taxonomic investigations of Selaginella can be improved. First leaves and spores should be prepared in permanent mountant (e.g. Hoyer's solution) for accurate observation of size, shape, and epidermal patterns. Secondly, data should be collected on a wide range of features.