Tree ferns, terrestrial. Stem black, erect, dictyostelic, covered with stubs of persistent frond bases, apex densely scaly; scales dark brown, narrowly triangular-lanceolate, entire. Fronds tufted, shortly stipitate; stipe scaly; lamina bipinnatifid, elliptic-lanceolate in outline, narrowed downward, papery, both surfaces glabrous, apex acuminate; pinnae pinnatifid, oblong-lanceolate, base decurrent to narrow rachis wing with triangular lobes between pinnae, apex acuminate; lower pinnae much shorter, basal ones triangular auricles; lobes oblong or triangular-oblong, margin entire, apex acute; veins free, pinnate, secondary veins 2- or 3-furcate, not reaching lamina margin; rachis and costae grooved adaxially. Fertile lamina as large as sterile lamina, slightly narrowed, pinnae caudate. Sori linear, costal, adjacent and parallel to costules on straight unbranched fertile veins parallel to costa; indusia facing toward costa, thin, covering young sporangia, opening when mature; spore reniform.

The genus Diploblechnum is an ingroup of Blechnum (R. Cranfill, Y. Nakahira & M. Kato, unpubl. data), although the two are distinct morphologically.

One species: Taiwan and SE Asian and Pacific islands.

(Authors: Wang Faguo (王发国), Xing Fuwu (邢福武); Masahiro Kato)