On the peristomes of the corticolous African species of Fissidens Hedw. (Fissidentaceae, Bryophyta)

The peristomes of 18 corticolous African Fissidens Hedw. species are described in detail and illustrated with light microscope images. Seventeen belong to F. subgen. Polypodiopsis sect. Antennidens and one to F. subgen. Neoamblyothallia. Most of these peristomes are imperfect. Compared to their presumed ancestral types, they are shorter, narrower, stiffer, undivided, deeply divided or irregularly divided, and in having a reduced hygroscopic capacity. Other sporophytic traits frequently found together with these anomalous peristomes are: narrow, cylindrical capsules with narrow, oblong exothecial cells; short and often papillose setae; and short opercula. Based on literature a strong relation is demonstrated between a corticolous life-style and anomalous peristomes for F. subgen. Polypodiopsis and F. subgen. Neoamblyothallia, whereas in the type subgenus anomalous peristomes are often connected with an aquatic habitat.