Didymochlaenaceae Ching ex Li Bing Zhang & Liang Zhang,, 2015

Zhang, Li-Bing & Zhang, Liang, 2015, Didymochlaenaceae: A new fern family of eupolypods I (Polypodiales), Taxon 64 (1), pp. 27-38 : 64

Didymochlaenaceae Ching ex Li Bing Zhang & Liang Zhang, fam. nov. – Type: Didymochlaena Desv.

Diagnosis. – Didymochlaenaceae are similar to Dryopte­ ridaceae in having rhizomes and petioles with scales, petioles with three or more vascular bundles arranged in a semi­circle, perispores with tuberculate folds, and a chromosome number of x = 41, but Didymochlaenaceae have elongate sori, while Dryopteridaceae have rounded sori.

Terrestrial ferns with short, erect, subarborescent, dic- tyostelic rhizome bearing long, narrow and small, subentire, hair­like scales and ± persistent petiole bases. Leaves tufted, large, monomorphic, firmly herbaceous, long­petiolate. Petiole stramineous, at least the base ± persistently scaly, adaxially grooved, not articulated, with three or more vascular bundles arranged in a semi­circle. Lamina bipinnate (Fig. 1 A), oblong­ ovate, anadromous or isodromous; neither upper nor lower pinnae reduced, apical pinna conform. Rachis and costa with very narrow scales, adaxially grooved. Pinnules dimidiate, somewhat rectangular, subsessile, at least the basal ones articu- lated at the base, apex rounded, basal margins thickened. Upper pinnules abruptly reduced and confluent. Midrib near the pos- terior margin or diagonal, weakly developed, not grooved. Lat- eral veins free, forked, with clavate ends before reaching sub­ entire to crenate margins (Figs. 1D, 2A–C). Sori elliptic­oblong (Figs. 1B, 2A–G), terminating a vein, indusiate, often some- what sunken in blade, forming bumps on adaxial side (Fig. 1C); margins of fertile leaves often sterile. Indusia elongate, cen- trally attached along a line, opening on either side. Receptacle elongate, bearing sporangia on both sides and around its distal extremity. Sporangia long­stalked (Fig. 2J). Spores monolete, ellipsoidal to globose, tuberculate and echinate on perispore (Fig. 1E). Chromosome number x = 41 (Manton, 1954; Smith & Foster, 1984; Walker, 1985).

A monogeneric family containing only one (Didymo- chlaena truncatula (Sw.) J.Sm.) or more species with nearly pantropical distribution, but not in Australia.

Both Hooker (1842: pl. 120) and Ching (1940) described the spores of Didymochlaena as trilete. Ching (1940) further reported that the spores have no perispores. These statements are incorrect (see our Fig. 1E).