ABSTRACT
The chapter investigates the extent to which spore characters are of value in taxonomic revision and classification of the genus Asterella. Using mainly scanning electron microscopy, spores of seventeen species of the genus are illustrated and classified into eight 'Spore Types' based on colour, primary sculpturing of the distal surface, shape and similarity of proximal and distal sculpturing. Only minor variation in spore ornamentation is observed between different populations of individual species, and most of the species studied can be readily identified on spore characters. Many of the observed differences between spores of different Asterella species are very striking indeed and provide excellent taxonomic characters. In many other liverwort genera the range of spore types is much narrower, even in other Marchantiales such as Marchantia and Plagiochasma. Asterella may therefore be considered as outstanding within the Bryophyta in the taxonomic value of the spores.
