Adiantum capillus-veneris
Adiantum jordanii
black maidenhair fern, common maidenhair, southern maiden-hair, southern maidenhair fern, Venus hair, Venus hair fern, Venus's-hair fern
adiantum, California maidenhair, California maidenhair fern
short-creeping;
scales golden brown to medium brown, concolored, iridescent, margins entire or occasionally with single broad tooth near base.
short-creeping;
scales reddish brown, concolored, margins entire.
lax-arching or pendent, closely spaced, 15–75 cm.
arching or pendent, clustered, 30–45 cm.
0.5–1.5 mm diam., glabrous, occasionally glaucous.
1–1.5 mm diam., glabrous, not glaucous.
lanceolate, pinnate, 10–45 × 4–15 cm, glabrous, gradually reduced distally;
proximal pinnae 3(–4)-pinnate;
rachis straight to flexuous, glabrous, not glaucous.
lanceolate, pinnate, 20–24 × 8–10 cm, gradually reduced distally, glabrous;
proximal pinnae 3(–4)-pinnate;
rachis straight, glabrous, not glaucous.
various, generally cuneate or fan-shaped to irregularly rhombic (plants in American southwest occasionally with segments nearly round), about as long as broad;
base broadly to narrowly cuneate;
margins shallowly to deeply lobed, incisions 0.5–7 mm, occasionally ± laciniate, sharply denticulate in sterile segments;
apex rounded to acute.
fan-shaped, not quite as long as broad;
base truncate or broadly cuneate;
margins of fertile segments unlobed but very narrowly incised, sterile segments with margins lobed, denticulate;
apex rounded.
transversely oblong or crescent-shaped, 1–3(–7) mm, glabrous.
transversely oblong, 3–10 mm, glabrous.
mostly 40–50 µm diam. 2n = 120.
mostly 40–50 µm diam. 2n = 60.
stalks 0.5–3.5 mm, dark color extending into segment base.
stalks 1–4 mm, with dark color ending abruptly at segment base.
Adiantum capillus-veneris
Adiantum jordanii
No evident pattern to morphologic variation in the species is discernible, although a number of segregate species and infraspecific taxa have been recognized within North American Adiantum capillus-veneris. In the Eastern Hemisphere, the species is diploid, with 2n = 60 (I. Manton 1950). Several tetraploid counts have been reported from North America (W. H. Wagner Jr. 1963). Spore-measurement data suggest, however, that the polyploid cytotype may not be widely distributed. Further investigation is needed to determine whether Adiantum capillus-veneris populations in North America are conspecific with those in Eurasia and Africa.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Adiantum jordanii occasionally hybridizes with A. aleuticum where their ranges overlap in northern California, yielding the sterile hybrid Adiantum × tracyi C. C. Hall ex W. H. Wagner. Adiantum × tracyi, morphologically intermediate between its parental species, can be distinguished from A. jordanii by its broadly deltate leaf blade that tapers abruptly from the 4(–5)-pinnate base to a 1-pinnate apex. It is best separated from A. aleuticum by leaf blades with a strong rachis, and by ultimate blade segments that are less than twice as long as broad. Adiantum × tracyi shows 59 univalents at metaphase; its spores are irregular and misshapen (W. H. Wagner Jr. 1962).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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