Geheebia Schimp.

The following generic description is based on N.Z. species.

Plants minute to c. 8 mm tall. Stem in cross-section with central strand and sclerodermis. Leaves erect-spreading when moist, erect and little altered, erect-incurved or weakly shrivelled when dry, with apices of at least upper leaves rounded; upper laminal cells with 1–3 low, rounded papillae or apparently smooth. Costa concolorous, failing 4–12 cells before apex; abaxial superficial cells quadrate to short-rectangular distally. Axillary hairs of 2–5 cells, of which the basal cell is shorter and brown. Laminal KOH colour reaction yellow to yellow-orange.

Dioicous. Perigonia bulbiform. Setae slender, red below, pale above, 3–10 mm. Peristome present or absent.

Geheebia was erected as a monotypic genus to accommodate Geheebia gigantea (Funck) Boulay (syn. G. cataractarum). It was extended by Zander (2013) to encompass species in Didymodon sect. Fallaces. This resulted in nine new combinations. Sequencing data from both nuclear and chloroplast DNA (Jiménez et al. 2022) supported six of these in a "Geheebia" clade, together with five other species, all previously regarded as species of Didymodon. The South African Geheebia ceratodontea (as Didymodon ceratodonteus) was earlier synonymised with the widespread and very variable Geheebia tophacea (as D. tophaceus) by Jiménez et al. (2005). In a N.Z. context G. tophacea and G. ceratodontea are morphologically distinct, and both are accepted here.