Asplenium ×biscayneanum

(D. C. Eaton) A. A. Eaton

Fern Bull. 12: 45. 1904

Common names: Biscayne spleenwort
Basionyms: Asplenium rhizophyllum var. biscayneanum D. C. Eaton Bull. Torrey Bot. Club 14: 97, plate 168. 1887
Treatment appears in FNA Volume 2.
Roots proliferous. Stems erect, not branched; scales blackish throughout, linear-deltate, sparse, 1–1.3 × 0.1–2.4 mm, margins entire. Leaves nearly monomorphic. Petiole green, becoming blackish in older leaves, 1–5(–12) cm, 1/8–1/3 length of blade; indument of black, narrowly lanceolate scales. Blade dull, linear, 2-pinnate, (4–)12–22 × 1–3.5 cm, papery, glabrous; base slightly tapered; apex narrowing gradually, not rooting. Rachis mostly blackish, green distally and in juvenile leaves, shiny, sparsely scaly. Pinnae in 9–20 pairs, oblong, 0.5–2 × 0.4–1.3 cm; apex blunt to truncate. Pinnules of 1–2 segments; segments linear-oblong, 3–6 × 1–3 mm; margins dentate; apex notched, pointed, rounded, or blunt. Veins free, evident. Sori 1–2 per segment, on both basiscopic and acroscopic sides. Spores abortive. 2n = ca. 180.

Habitat: Hammocks, on limestone rock faces
Elevation: 0–20 m

Discussion

Asplenium × biscayneanum is the hybrid of A. trichomanes-dentatum and A. verecundum, with which it occurs. This peculiar spleenwort may most readily be separated from A. trichomanes-dentatum by its deeply cut pinnae, and from A. verecundum by being only 2-pinnate and having long petioles. Chromosome pairing in A. × biscayneanum is irregular. Judging from herbarium collections, it shows considerable hybrid vigor. All the collections are from Dade County, Florida, where it may now be extirpated.

References

None.

Lower Taxa

No lower taxa listed.