Aspleniaceae
English: Spleenworts.
Genera: 2: Asplenium, Hymenasplenium.
Clades: Aspleniidae; Polypodiopsida; Pteridophyta; Plants.
Region: worldwide.
Habitat: temperate and tropical.
Botany
Identification: elongated; unpaired sori.
Ferns.
Root: rhizomes, creeping or somewhat erect, usually unbranched, with scales, usually have a lattice-like, clathrate structure.
Leaves: undivided or divided, with up to four-fold pinnation; petioles have two vascular bundles, uniting to form an X-shape in cross-section towards the tip of the leaf; stalks of the sporangia are one cell wide in the middle.
Sori: elongated; unpaired, rarely in pairs on a single vein, never curving over the vein; indusium flap-like, along one edge of a sorus.
Taxonomy
Aspleniaceae have been subject to considerable changes. The narrow circumscription of Aspleniaceae contains only two genera. A very broad Aspleniaceae includes 10 other families, which can be named Aspleniales.
Aspleniaceae was first described by Edward Newman in 1840, with three genera: Athyrium, Asplenium and Scolopendrium. Athyrium is now placed in a different family, Athyriaceae, not considered very strongly related to the Aspleniaceae, and Scolopendrium is regarded as synonym of Asplenium. Asplenium has previously been split into a dozen or so genera. Modern consensus of molecular phylogenetic studies is that all are nested within Asplenium. Christenhusz and Chase had proposed a much broader circumscription of Aspleniaceae, in which it consisted of all the separate families that PPG I places in the suborder Aspleniineae (eight at the time), with the families reduced to subfamilies. Thus the Aspleniaceae of PPG I became the subfamily Asplenioideae.