Didymoglossum, Desv. (Desvaux, 1827

Ahamada H. Saïd, Sabine Hennequin, Germinal Rouhan & Jean-Yves Dubuisson, 2017, Disentangling the diversity and taxonomy of Hymenophyllaceae (Hymenophyllales, Polypodiidae) in the Comoros, European Journal of Taxonomy 313, pp. 1-53 : 20

Notes on genus Didymoglossum in Comoros

Didymoglossum lorencei , D. robinsonii and D. erosum are new for the archipelago. They were never reported, likely due to confusions with morphologically close taxa. We can, however, note here that D. erosum , absent in the archipelago according to Tardieu-Blot (1951) and Roux (2009), would be nevertheless present according to the type of Trichomanes erosum var. laciniatum which would have been collected in Comoros. But this type specimen could not be observed nor studied, and its identification remains questionable. Sterile D. erosum is also indeed easily confused with small sterile D. cuspidatum . The confusion is also easy between D. rotundifolium and small D. erosum specimens with entire laminae. The first species never displays lobed fronds contrary to the second. Didymoglossum lorencei and D. robinsonii are often found growing as epiphyte and mixed and confused with other species of Didymoglossum . Only microscopic observation of marginal hairs allows the distinction. It explains that the occurrence of D. lorencei in La Réunion has been reported only recently, because the species is quite discrete and mostly grows on tree-fern trunks in association with the much more abundant D. cuspidatum (pers. obs.; Grangaud 2010).