Asplenium diellaciniatum (no common name, NCN), a terrestrial or epipetric (growing on rocks) fern in the spleenwort family (Aspleniaceae), is endemic to Kauai. Stipes (blade stalk) and rachis (midrib) are shiny, black or purple-black to maroon. Blades are one- to two- (sometimes three-) pinnate (rows on either side of the axis), pinnae entire to shallowly or deeply pinnatifid (cut) or pinnate. The veins are mostly free and seldom anastomosing (joining) near coastae (vein) to form a layer of areoles (space enclosed by vein). Population studies of A. diellaciniatum reveal an amazing range of variation in leaf morphology and degree of lobing. This species is represented with extremely variable frond morphology and dissection, depending on age and stage of development of the plant and possibly also microhabitat.