Comparative morphology and rhizome anatomy of two new species of Zygophlebia (Grammitidaceae) from Madagascar and notes on the generic circumscription of Zygophlebia and Ceradenia

The recognition of two new Malagasy species of Grammitidaceae, Zygophlebia goodmanii and Z. anjanaharibensis, puts into question some morphological and anatomical features separating the related genera Zygophlebia and Ceradenia, which until now were mainly defined based on neotropical taxa. The two new species share with Zygophlebia and Ceradenia subgen. Filicipecten a rhizome with dorsiventral symmetry and an amphiphloic siphonostele, well‐differentiated phyllopodia, a deeply pinnatifid lamina without hydathodes at the tips of veins, and glandular receptacular paraphyses. Because of the non‐waxy translucent exudates of their paraphyses, the two new taxa are placed in the genus Zygophlebia, in spite of their mostly free leaf veins. Peculiar vascular gaps, unrelated to phyllopodial insertions and distinctive of Zygophlebia, are found in the rhizome stele of Z. goodmanii. The lack of setiform hairs and the distal sori location in Z. anjanaharibensis do not allow for linking this species to any of the three groups previously described by Bishop in Zygophlebia.