ON THE PERISTOME TYPES FOUND IN THE FISSIDENTACEAE AND THEIR IMPORTANCE FOR THE CLASSIFICATION

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  Based on a study of peristomes of about 200 species of all subgenera and sections of the Fissidentaceae, 5 basic types of peristome are recognized: the bryoides-type, the scariosus-type, the zippelianus-type, the similiretis-type and the taxifolius-type. The scariosus-type is correlated with 28-40, but mostly circa 32 exothecial cells on the capsule periphery. The number of exothecial cells found with the other types is typically more than 40. The bryoides-type of peristome is characteristic of F. sect. Fissidens, F. subg. Sarawakia and the genus Nanobryum. It also appears that these taxa arc gametophytically more similar to each other than to any other taxon, except that F. subg. Sarawakia is intermediate between F. subg. Octodiceras and sect. Fissidens. The scariosus-type of peristome is characteristic of F. subg. Aneuron, and the F. subg. Fissidens sections Areofissidens, Aloma, Pycnothallia, Semilimbidium and Crenularia. Within this group Aneuron and Areofissidens are gametophytically very similar, and so are Pycnothallia, Semilimbidium and Crenularia. The zippelianus-type of peristome is characteristic of F. sect. Crispidium; the similiretis-type of peristome is characteristic of F. sect. Amblyothallia and the taxifolius-type of peristome is characteristic of F. sect Serridium. Several other peristome forms were also found; these, however, occur in one or just a very few species and are not characteristic of any supraspecific taxon.