Adiantum pulverulentum L.

Authority

Mickel, John T. & Smith, Alan R. 2004. The pteridophytes of Mexico. Mem. New York Bot. Gard. 88: 1-1054.

Family

Pteridaceae

Scientific Name

Adiantum pulverulentum L.

Description

Species Description - Rhizomes short-creeping, 4–8 mm diam.; rhizome scales dark brown, 1.5–2.5 x 0.3–0.8 mm, linear-lanceolate, with marginal hairs 0.1–0.3 mm long; fronds clumped, 40–105 cm long, arching; stipes atropurpureous, lustrous, 20–55 cm x 2–5 mm, ca. 1/2– 2/3 the frond length, with small (to 3 mm long), brown, pectinate scales; blades deltate, 2-pinnate, (20–)25–50 cm wide, each blade with a conform terminal pinna; rachises atropurpureous, with rather dense tan lanceolate scales and hair-like scales; pinnae 3– 8(–10) pairs, alternate, gradually tapering at the tips, stalked 3– 8 mm; pinnules dimidiate, oblong, largest 10–20 x 4–6 mm, fertile pinnules obtuse or blunt, straight, or the apices (beyond sori) curved toward pinna tips, sterile pinnules acute, falcate, coarsely serrate, terminal pinnule of each pinna non-conform, elongate, proximal pinnules reduced and deltate, non-articulate; veins free, forking, ending in teeth in sterile pinnules; indument adaxially absent, abaxially usually of narrow tan scales 0.8 mm long, blades not glaucous; idioblasts present on both blade surfaces; sori generally one per pinnule (infrequently with 1 or 2 smaller sori distal to the linear main one), confined to acroscopic margins; indusia 5–10 mm long, linear, glabrous; 2n=60, 90 (Jam).

Discussion

Lectotype (chosen by Proctor, 1977: 185). Plumier, Descr. Pl. Ame´r., pl. 47, 1693 (=Traite´ Foug. Ame´r., t. 55, 1705), based on a plant from Martinique or Hispaniola.

?Adiantum monotis Nees, Linnaea 19: 684. 1847. Type. Mexico. Aschenborn 348 (B?). This was placed as a synonym of A. villosum by Lellinger (1989: 159), but based on the description, it seems more likely to be A. pulverulentum; no one recently has examined the type. For additional synonymy, see Lellinger (1989: 153). This species is very common in lowland areas of Veracruz, Oaxaca, and Chiapas, but rare elsewhere in Mexico. Adiantum pulverulentum is distinctive among the short-pinnuled, bipinnate, idioblastic species in usually having one long sorus per pinnule, along the acroscopic margin (and occasionally at the distal end). Occasional specimens, especially those that are only partially fertile, have the sori somewhat lobed: Ver (Smith 2084, UC), Oax (Hallberg 1264, NY). Abortive-spored hybrids between A. pulverulentum and A. villosum (Fig. 8F) have large, acute pinnae, one sorus per pinnule, and glabrous indusia: Ver (Mickel 7226b, NY, UC; Purpus 7765, UC, US), Oax (Conzatti et al. 31475, US; Mickel 5777, NY, UC, Fig. 41F), Chis (Breedlove 38671, DS, ENCB; Fisher 35400, NY). Another probable hybrid involving A. pulverulentum is Breedlove 34993 (DS), from Chiapas. This hybrid may involve either A. tetraphyllum or A. decoratum as the second parent. This specimen has strongly malformed spores and variably continuous or discrete sori along the acroscopic pinnule margins.

Distribution

Terrestrial in wet forests at low elevations, lower montane rain forests, pine-oak-Liquidambar forests; 50–1000 (–1400) m. Mexico; Guat, Bel, Hond, Salv, Nic, CR, Pan; Gr & L Ant; Col, Ven, Trin, Guy, Sur, Fr, Gui, Ec, Peru, Braz, Bol.

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