Atti Accad. Sci. Siena 9: 231, plate 1. 1808.
Stems prostrate. Leaves loosely appressed when dry, spreading when moist. Capsule ovoid to pyriform, [0.3–]0.5–0.8[–1] mm.
North America, Mexico, West Indies, Central America, South America, Eurasia, Africa, Atlantic Islands, Pacific Islands (Hawaii, New Zealand), Australia.
Species ca. 11 (2 in the flora).
Fabronia is characterized by its very small size, ovate to oblong-lanceolate, long-acuminate, usually toothed leaves tipped with linear cells, rhomboidal laminal cells, and relatively short costa. However, because of the wide degree of morphological variability, especially within the F. ciliaris complex, Fabronia is taxonomically difficult. Discussions of Fabronia by H. A. Crum and L. E. Anderson (1981) and W. R. Buck (1994b) are enlightening with respect to taxonomic problems.