Sp. Pl.2: 1094. 1753; Gen. Pl. ed 5, 485. 1754
Nearly worldwide except at latitudes greater than 60°.
Most diverse in Andean South America, Adiantum is primarily a tropical genus; of the nine species occurring in the flora, A. melanoleucum, A. tenerum, and A. tricholepis are strictly subtropical. Adiantum hispidulum occurs only as an escape from cultivation. The genus is absent from dry areas in the interior of the continent.
Adiantum is a very clearly circumscribed genus of ferns, the character state "sporangia borne on abaxial surface of false indusium" being both necessary and sufficient to define it. Within this large and widespread genus, however, species relationships are mostly unknown. An evolutionary classification of the group is indeed much needed (R. M. Tryon and A. F. Tryon 1982).
Species ca. 150–200 (9 in the flora).
|1||Segments at middle of penultimate divisions of blades ± fan-shaped, rhombic, transversely oblong, or nearly round, about as long as broad.||> 2|
|1||Segments at middle of penultimate divisions of blades ± oblong or long-triangular, at least 2 times as long as broad (rarely, reniform).||> 5|
|2||Dark color of stalks extending into base of ultimate segments.||Adiantum capillus-veneris|
|2||Dark color of stalks ending ± abruptly at base of ultimate segments.||> 3|
|3||Segment stalks terminating in small, cupulelike swelling at base of ultimate segments.||Adiantum tenerum|
|3||Segment stalks not terminating in small, cupulelike swelling at base of ultimate segments.||> 4|
|4||Ultimate segments glabrous.||Adiantum jordanii|
|4||Ultimate segments hirsute.||Adiantum tricholepis|
|5||Rachises hispid or strigose; blades pinnate (occasionally pseudopedate in Adiantum hispidulum).||> 6|
|5||Rachises glabrous; blades pseudopedate.||> 7|
|6||Ultimate segments with scattered multicelled hairs; rachises hispid; false indusia ± round.||Adiantum hispidulum|
|6||Ultimate segments glabrous; rachises strigose; false indusia crescent-shaped.||Adiantum melanoleucum|
|7||Segments at middle of penultimate divisions of blades ± oblong; leaves lax-arching, blades fan-shaped.||> 8|
|7||Segments at middle of penultimate divisions ± long-triangular or reniform; leaves arching to stiffly erect, blades fan-shaped to funnel-shaped.||> 9|
|8||Segments at middle of penultimate divisions of blades generally less than 3.2 times as long as broad, apices with rounded, crenulate or crenate-denticulate lobes, lobes separated by shallow sinuses 0.1–2(–3.7) mm, segment stalks ca. 0.6–0.9 mm.||Adiantum pedatum|
|8||Segments at middle of penultimate divisions usually more than 3.2 times as long as broad, apices with sharply denticulate, angular lobes, lobes separated by deep sinuses 0.6–4 mm, segment stalks to 0.6 mm.||Adiantum aleuticum|
|9||Central ultimate segments on stalks less than 0.9 mm; false indusia mostly less than 3.5 mm.||Adiantum aleuticum|
|9||Central ultimate segments on stalks generally greater than 0.9 mm; false indusia mostly exceeding 3.5 mm.||Adiantum viridimontanum|
|Author||Cathy A. Paris +|
|Common name||Maidenhair fern +|
|Etymology||Greek adiantos, unwetted, for the glabrous leaves, which shed raindrops +|
|Illustrator||John Myers +|
|Reference||fernald1950a +, paris1988a +, paris1991a + and wagner1956a +|
|Taxon name||Adiantum +|
|Taxon parent||Pteridaceae +|
|Taxon rank||genus +|
|Volume||Volume 2 +|