New or little-known epiphyllous liverworts, XXIII. Radula pinnata (Radulaceae), a new species from Madagascar

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  Radulaceae is a family occurring in all continents but Antarctica, with its only genus Radula Dumort., containing more than 200 species. A peculiar new species was found in the Mananara North Biosphere reserve and National Park in the northeast of the island of Madagascar. The new species, although I have found exclusively on living leaves, does not show the morphologic characters of the artificial section Radula sect. Epiphyllae Castle ex Grolle (tiny plants, stem with single, unpigmented cortical layer and thin walled medullary cells and production of abundant sporophytes or gemmae). It is a robust, sterile plant with much thicker stem, 12–15 cells wide, consisting of somewhat thickened, slightly pigmented cortical and medullary cells. The most characteristic feature is the very regularly densely pinnate (to bipinnate) branching system with closely imbricate leaves. The leaves are not caducous, and the leaf cells bear a smooth cuticle. The lobule is quadrangular with an obtuse or apiculate apex, about half the length of the lobe. The new species bears a superficial resemblance to R. appressa Mitt., a widespread African species and to an unclarified taxon: R. silvestris Gottsche, described from Madagascar. From these the new species is distinguished by the above-mentioned characteristics.