by Angelo Troia, Germinal Rouhan
To stabilize the application of some names in the genus Isoetes in the Mediterranean biodiversity hotspot, we studied herbarium specimens and imaged spores with scanning electron microscopy, with special reference to those taxa in the I. longissima Bory and I. histrix Bory groups that were described from France, Algeria and Turkey, and are in need of a taxonomic revision. The following names are lectotypified: I. adspersa A.Braun, I. boryana Durieu, I. delalandei J.Lloyd, and I. viollaei Hy. Holotypes of I. perralderiana Durieu & LeTourn. ex Milde and I. olympica A.Braun were ascertained. We conclude that I. boryana (listed in the 'Bern Convention' and in the European Union 'Habitats' Directive) justifies consideration at species rank, but I. adspersa should be synonymized with I. longissima. Isoetes tenuissima Boreau and I. perralderiana are proposed as distinct species pending further studies. In the I. histrix group, we tentatively accept I. delalandei as a species, presenting some observations on I. histrix f. subinermis Durieu nom. nud. The latter might also represent a distinct species.