Microsorum

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Microsorum

Distribution

Paleotropical, extending to E Australia and New Zealand, eastwards to most tropical islands in the Pacific: present
Paleotropical, extending to E Australia and New Zealand, eastwards to most tropical islands in the Pacific.

Taxonomy

Microsorum is closely related to Leptochilus, the only difference being in the arrangement of the sori. Lepisorus is very similar and here distinguished mainly for practical reasons. It can be recognised by the constant combination of sori in a single row between costa and margin and peltate paraphyses. In Microsorum, the species with a similar, single row of sori lack peltate paraphyses. In this circumscription, Microsorum is almost certainly not a monophyletic group, and should minimally be made to include Leptochilus in order to be monophyletic. A more complete revision of Lepisorus and related ferns is necessary to assess whether Microsorum and Leptochilus together form a monophyletic group within the lepisorioid ferns or whether the opposite is more likely.

Important characters within Microsorum are found in the rhizome scales, the presence or absence of sclerenchyma in the rhizome, the disposition of the sori and the venation pattern. Especially this last character shows a considerable variation, but a full evaluation of its value requires still more knowledge about ontogeny and development of the patterns.

Nooteboom arranged the species in a number of groups, mainly based on soral disposition and venation pattern. More properly, his groups should be considered as morphological types, as several species are included in more than one of the groups. A satisfactory systematic subdivision of Microsorum is still lacking.

Citation

Bosman - in Leiden Bot. Ser. 1991: 69
Hennipman et al. - in Kramer & Green, Fam. & Genera Vasc. Pl. 1. 1990: 219
Noot. - in Blumea. 1997: 294
Hennipman et al. - in Kramer & Green, Fam. & Genera Vasc. Pl. 1. 1990: 219
Hennipman et al. - in Kramer & Green, Fam. & Genera Vasc. Pl. 1. 1990: 221