Bolbitis is a genus of ferns belonging to the family Dryopteridaceae (subfamily Elaphoglossoideae), placed in the order Polypodiales under the Pteridophyte Phylogeny Group classification of 2016 (PPG I). The genus was established by Heinrich Wilhelm Schott in 1835 and encompasses roughly 85–90 accepted species, with several earlier genus names — including Campium, Egenolfia, and Poecilopteris — now treated as synonyms.
Members of Bolbitis are terrestrial or semi-aquatic ferns found predominantly in the tropics and subtropics of Africa, Asia, and the Americas. They typically grow along stream banks, on rocks, or submerged in flowing water, anchored by threadlike rootlets arising from creeping rhizomes. Fronds are pinnate to bipinnate with dark green blades; fertile and sterile fronds are often dimorphic in form.
The genus includes notable species adapted to fully aquatic conditions. Bolbitis heudelotii, the African water fern or Congo fern, is native to tropical and subtropical Africa from Ethiopia to Senegal and south to northern South Africa, where it grows submerged in rivers and streams with fast, clean, slightly acidic water. Bolbitis heteroclita, native to Asia, grows at the margins of water bodies and also tolerates full submersion. Both species are widely cultivated as aquarium plants in tropical freshwater tanks.
Distribution
Bolbitis species occur primarily across the tropics and subtropics of Africa, Asia, and the Americas. B. heudelotii ranges across tropical and subtropical Africa from Ethiopia and Senegal south to northern South Africa. B. heteroclita is distributed in tropical Asia. Many species grow along streams and rivers, on rocks, or in seasonally flooded margins of water bodies.
Ecology
Species in Bolbitis typically inhabit stream margins, rocky riverbanks, and the beds of fast-flowing water bodies in humid tropical and subtropical environments. B. heudelotii grows submerged in rivers and streams, anchored to rocks or woody substrate by rhizome rootlets; its native habitat features fast-moving, very clean, slightly acidic, and not very hard water over sandy or rocky bottoms.
Cultivation
Bolbitis heudelotii is one of the most commonly cultivated species in tropical freshwater aquaria, often used as a midground specimen. It requires water temperatures of 20–28 °C and moderately soft to neutral water with a pH of 5.0–7.0. It does best in flowing water and a shaded position; supplemental CO₂ supports growth. It is best grown attached to wood or rock rather than planted directly in substrate. Propagation is by division of the rhizome; it is a slow-growing species. B. heteroclita is similarly cultivated as a submerged or marginal aquarium plant.
Taxonomy Notes
Bolbitis was described by Heinrich Wilhelm Schott in 1835 (Gen. Fil. t. 14), with Bolbitis serratifolia (Mert. ex Kaulf.) Schott as the type species (lectotype designated by Christensen in 1906). Several genera described around the same period are now treated as heterotypic synonyms, including Campium C.Presl, Egenolfia Schott, Poecilopteris C.Presl, and Cyrtogonium J.Sm. The genus is placed in subfamily Elaphoglossoideae of Dryopteridaceae under PPG I (2016).
