From the Greek diplazios which means double, because indusia lie on both sides of the vein.
Rhizome: creeping to erect, scaly.
Frond: deciduous or evergreen, trophopod, monomorphic or weakly dimorphic.
Stipe: green, deeply grooved above, swollen or not at base, scaly or glabrous, vascular bundles: 2, lunate.
Blade: 1-2 pinnate (entire), oblong-lanceolate to deltate, herbaceous to papery.
costae U-grooved above, continuous from rachis to costae, segments entire, crenulate, or serrate, veins free or netted.
Sori: linear, basal sori paired back-to-back on the same vein, indusium: linear, persistent, sinus, sporangia: brownish.
Diplazium is very close to Athyrium, but the sori never hook over the veins, and are sometimes paired back-to-back. Additionally, the grooves in the rachis are U-shaped vs. V-shaped in Athyrium. Differs from Deparia in having the grooves continuous from costa to rachis.
Diplazium sibericum. A characteristic on the visible level distinguishing Diplazium from Athyrium is back-to-back sori.
Illustration from Scandinavian Ferns by Benjamin Ĝllgaard and Kirsten Tind, Rhodos, 1993.