This species with a mainly western Mediterranean distribution is present in Sardinia and in all Tyrrhenian regions of Italy, from Liguria to Sicily. The life-cycle can be spent part in water, part on moist to dry soil. It grows in wet meadows, in pools and ephemeral ponds that are flooded in winter and spring, but generally dry in summer, on acid soils, usually on siliceous substrates, from sea level to about 900 m. In Sardinia this is the rarest species of the genus, indicated in the IUCN regional Red List as a critically endangered taxon (Conti et al., 1997). The genus name derives from the Greek 'isos' (equal) and 'ethos' (year), in reference to the leaves that persist throughout the year; the species is dedicated to the French botanist Michel Charles Durieu de Maisonneuve (1796-1878) author of a Flora of Algeria. Sporulation period: March to May.

Italian name(s): Calamaria di Durieu (Italia), Isoete di Durieu (Italia).