Roots not proliferous. Stems ascending to erect, rarely branched; scales dark brown to blackish throughout, narrowly deltate, 2--4 × 0.25--0.45 mm, margins entire. Leaves weakly subdimorphic, fertile leaves taller and more erect than sterile leaves. Petiole reddish or purplish brown throughout, lustrous, 1--10 cm, 1/5--1 times length of blade; indument of dark brown to black scales, narrowly deltate at very base, grading into hairs distally. Blade highly variable and typically irregularly shaped, narrowly deltate to lanceolate, pinnatifid or 1-pinnate in proximal 1/3, 2--20 × 1--6(--13) cm, medium thick, sparsely pubescent adaxially only; base ± truncate; apex acute to long-attenuate, apical buds borne occasionally but not known to root in nature. Rachis reddish or purplish brown abaxially, fading to green distally, lustrous, glabrous. Pinnae in 0--3 pairs, often irregular in size and shape, deltate to narrowly deltate; proximal pinnae 5--30(--80) × 3--10(--15) mm; base truncate to obtuse, auriculate on both sides; margins entire to finely serrate or crenulate; apex obtuse to acute or occasionally attenuate. Veins somewhat evident, mostly free, rarely anastomosing. Sori 1--10(--15+) pairs per pinna, on both acroscopic and basiscopic lobes. Spores malformed (sterile form) or 64 per sporangium (fertile form). 2 n = 72, 144. Conglomerate boulders; 70 m; Ala. The above description applies to the sterile hybrid Asplenium platyneuron × rhizophyllum and its allopolyploid derivative. The allotetraploid form is known only from Hale County, Alabama, where it occurs with A . platyneuron (but not with A . rhizophyllum ) on conglomerate boulders (K. S. Walter et al. 1982). The sterile diploid form of A . ebenoides occurs at elevations of 70 to 500 m within the region where the ranges of the parental species overlap, always occurring with both parents on limestone, sandstone, or other rock strata. A hybrid between the allopolyploid and A . platyneuron [ A . × boydstoniae (K. S. Walter) J. W. Short] was discovered at Havana Glen. An unnamed hybrid between the sterile diploid (presumably via unreduced spores) and A . rhizophyllum is known from West Virginia and Missouri (K. S. Walter et al. 1982).
From Flora of Indiana (1940) by Charles C. Deam
This fern is a hybrid between Asplenium platyneuron and Camptosorus rhizophyllus. (Slosson. Bull. Torrey Bot. Club. 29: 487-495. 1902.) Three colonies of this hybrid were discovered in Lawrence County by Ralph M. Kriebel who fully described them in Amer. Fern Jour. 23: 52-59. 1933. Mr. Kriebel is one of the best amateur botanists Indiana has ever had, and it is to his discriminating collecting that we owe not only an authentic Indiana record of this hybrid fern but also the records of three hybrid oaks and many other rare plants of Lawrence County.