A synoptic revision of the genus Blechnum L. in Madagascar.

The genus Blechnum L. in Madagascar has been the subject of two previous taxonomic treatments (Christensen 1932; Tardieu-Blot 1960) but, following the intensive collecting of specimens that has marked the 1980–2000 period and that continues today, an update to these treatments has become necessary. This new treatment includes four new species, two new synonyms, a new combination, a lectotypification and the description of three putative hybrids. The hypothesis of hybridization between several taxa of Blechnum, the only explanation that can account for the existence of intermediate forms, otherwise unclassifiable, is discussed. A new key is presented for the identification of the 16 species and varieties currently recognized on the island, as well as distribution maps and illustrations of the new taxa. Complementary descriptions and illustrations are also provided for certain earlier-published species for which infraspecific variability was not adequately understood or where different juvenile and adult forms have been confused.