Syn. Cystoseira spinosa Sauvageau 1912; Cystoseira adriatica Sauvageau 1912
Dark-brown, single-axis algae that resembles a small tree, up to 40 cm tall. The cauloids can either be simple or complex, with smooth, but occasionally warty texture. Branches can be cylindrical or spinose and all are lost during the estivation period from summer to autumn. The only species in the area that forms tophules; bulge-like growths from which young branches grow. Fertile from winter to early summer.
Subtidal sheltered or semi-exposed areas, from 4-15m deep.
Presumably still common but showing signs of regression due to multiple environmental and anthropogenic factors. Distribution not well studied, but plentiful washed-up specimens suggest sizable populations along the Istrian coast.
- Gongolaria montagnei var. compressa (Ercegović) Verlaque, Blanfuné, Boudouresque & Thibaut 2022 – flattened upper branches
- Gongolaria montagnei var. tenuior (Ercegović) Molinari & Guiry 2020 – spiny upper branches