Platyhypnidium mutatum, a mysterious new moss from Germany

Abstract

Platyhypnidium mutatum Ochyra & Vanderpoorten (Brachytheciaceae) is described and illustrated as a new moss species. It is known from a single locality in a waterfall at Allerheiligen in the Black Forest in southwestern Germany. This is an aquatic moss closely related to P. riparioides (Hedw.) Dixon but easily recognized by its irregularly 1–3-stratose laminae with 3–5-stratose, often broad ridges irregularly scattered throughout the leaf lamina, the strong single, but frequently spurred, percurrent costa, the plane or inflexed leaf margins which are serrulate throughout or only weakly so to entire above the base, and the linear-flexuose to oblong-hexagonal Iaminal cells. The species produces fully mature sporophytes which exhibit all typical features of the brachythecioid mosses including ecostate inner perichaetial leaves, relatively short, slightly inclined and asymmetric capsules, obliquely long rostrate operculum, round-pored stomata, redbrown exostome teeth, perforated endostome processes, and appendiculate cilia.