Radula demissa M. A. M. Renner

South-eastern Australia in Victoria and Tasmania, and New Zealand. On mainland Australia Radula demissa occurs only on tablelands and highlands in southern and eastern Victoria, but in Tasmania the species is widespread. Radula demissa grows in cool temperate and warm-temperate rainforests and occasionally in wet sclerophyll forests, particularly in the southern part of its range. In New Zealand Radula demissa occurs throughout all three main islands, and extends east to the Chatham Islands and south to the Auckland and Campbell Islands. It inhabits all forest environments, but is rare in coastal forests with high exposure to salt-laden winds. Radula demissa occupies a broad elevation range, from the coast to around 1600 m asl, where it grows in subalpine scrub above the treeline. In forests Radula demissa is typically an epiphyte on tree trunks, branches and twigs where it forms characteristic fan-shaped hanging wefts, and is frequently encountered in riparian areas and edge habitats where local light environments are brighter than adjacent forest interiors. Common host species in New Zealand include Melicytus ramiflorus and Beilschmiedia tawa. Radula demissa is also commonly encountered as an epiphyll on the leaves of ferns and broadleaved shrub and tree species. In New Zealand Hymenophyllum species, including Hymenophyllum demissum, Hymenophyllum ferrugineum and Hymenophyllum scabrum are favorite fern hosts, and Beilschmiedia tawa is a frequent broadleaf host. In lowland to montane podocarp-broadleaf forest of tall stature with sparse sub-canopy and shrub layers Radula demissa can be found as a trunk epiphyte and epiphyll on Beilschmiedia tawa, and as an epiphyll on leaves of Hymenophyllum demissum where this species grows in dense carpets on the forest floor. On bark Radula demissa is often associated with Radula allisonii, Radula plicata, Radula strangulata, Metzgeria spp. and various species of Lejeuneaceae including Drepanolejeunea aucklandica and Metalejeunea cucullata, Sematophyllaceae, various Plagiochilaceaespecies including Dinckleria pleurata, Frullania spp. Co-occurrence with phenetically similar species can pose a challenge to identification. On twigs Radula demissa grows with Plagiochila colensoi, Lepidolaena taylorii, Lepidolaena palpebrifolia, Radula plicata, and on leaves Radula demissa grows with Echinolejeunea papillata, Cololejeunea laevigata, and members of the Lejeunea epiphylla Colenso aggregate. In subalpine scrub Radula demissa occurs on damp rock and adjacent soil, sometimes in highly insolated microsites. Alpine plants exhibit some subtle morphological differences from forest plants, as discussed in the next section.

Radula demissa is a species of liverwort.