Asplenium adiantum-nigrum
Asplenium ×curtissii
black spleenwort
Curtiss' spleenwort, spleenwort
not proliferous.
proliferous.
ascending or short-creeping, infrequently branched;
scales dark brown to blackish throughout, narrowly deltate, 2–4(–5) × 0.2–0.5 mm, margins entire or shallowly denticulate to serrulate.
erect, unbranched;
scales blackish throughout, narrowly deltate, 1 × 0.2 mm, margins entire.
monomorphic.
monomorphic.
dark reddish brown proximally, often fading to green distally, lustrous, 2–20 cm, 2/3–2 times length of blade;
indument of black filiform scales and minute hairs.
brownish black, 3–10(–15) cm, 1/3–2/5 length of blade;
indument of blackish, narrowly lanceolate scales at base.
deltate, 2–3-pinnate, 2.5–10 × 2–6.5 cm, thick, hairs dark, scattered, minute;
base truncate;
apex acute to acuminate, not rooting.
oblong-lanceolate, 2-pinnate, 10–30 × (1.5–)5–10 cm, thin, glabrous;
base not or only slightly tapered;
apex gradually narrowing, not rooting.
in 4–10 pairs, deltate to lanceolate;
most proximal (largest) pinnae 1.5–4 × 1–2.5 cm;
base obliquely obtuse;
segment margins coarsely incised;
apex acute.
in (7–)14–22 pairs, oblong;
medial pinnae 1–6 × 0.5–1.5 cm;
base truncate;
apex pointed.
free, evident.
free, evident.
1–numerous pairs per pinna [1–6 pairs per segment], on both basiscopic and acroscopic sides.
1–4 per segment, usually more on acroscopic side.
64 per sporangium.
abortive.
greenish throughout or sometimes reddish brown proximally, lustrous, sparsely pubescent.
blackish to green, dull, nearly glabrous.
linear to fan-shaped to unequally pinnate, 3–9 × 1–7 mm, mostly notched apically.
= 144.
= 108.
Asplenium adiantum-nigrum
Asplenium ×curtissii
Asplenium adiantum-nigrum is principally a Eurasian species and occurs extremely rarely in North America (see M. G. Shivas 1969 and M. D. Windham 1983 for a discussion of the conspecificity of Western Hemisphere and Eastern Hemisphere material). It is an allotetraploid derived from hybridization of two European taxa, A. cuneifolium Viviani and A. onopteris Linnaeus (M. G. Shivas 1969). Hybrids involving A. adiantum-nigrum and other Asplenium species occur in Europe but are unknown in North America.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Asplenium × curtissii, sterile and with irregular meiosis, is the product of hybridization between A. abscissum and A. verecundum and occurs with them in central Florida, sometimes forming large colonies by root proliferation. It can readily be separated from A. abscissum by its pinnate blades. From A. verecundum it can be distinguished by its relatively long petioles and less divided blades. Asplenium × curtissi is known only from several localities in north central Florida. It makes a showy conservatory plant.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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