Mickel, John T. & Smith, Alan R. 2004. The pteridophytes of Mexico. Mem. New York Bot. Gard. 88: 1-1054.
Polypodiaceae
Genus Description - Epiphytic, occasionally epipetric or terrestrial; rhizomes shortto long-creeping; rhizome scales concolorous, brownish, often clathrate, surface glabrous, margins entire; fronds clumped to distant, monomorphic, sessile to long-stipitate, narrowly linear to elliptic, attenuate at apices and bases, articulate on phyllopodia; margins entire, modified; blades thin to usually thick, simple (in ours, rarely pinnate in a few extraterritorial species), glabrous (or sparingly hairy in a few extraterritorial spp.); venation areolate with 1 to usually several or many rows of areoles formed by anastomosing cross-veins from main lateral veins, the crossveins producing 2 (or sometimes more) excurrent, simple, free veins, a third excurrent vein sometimes completely bisecting the areole; sori round, exindusiate, non-paraphysate, at ends of free included veins, usually in 2 (to ca. 4) rows between main lateral veins; sporangia glabrous; spores bilateral, verrucate with spherical deposits; x=37.
Lectotype (chosen by J. Sm., Hist. Fil. 95. 1875): Campyloneurum repens (Aubl.) C. Presl [Polypodium repens Aubl.].
Campyloneurum is now usually segregated from Polypodium s.l. and includes approximately 50 neotropical species. It is characterized by the monomorphic, simple leaves (two species in South America are 1-pinnate), non-paraphysate sori borne on the free included vein tips, and usually clathrate, glabrous rhizome scales. There have been recent attempts at revision (Lellinger, 1988; Leo´n, 1992), but the genus is still inadequately understood. We depart in some respects from the circumscriptions adopted in both of those treatments, in particular with the species C. angustifolium and C. serpentinum. Several species, including C. phyllitidis, C. repens, and C. xalapense in Mexico, have been reported as having nectaries on the abaxial side of the blades (Mickel & Beitel, 1988; Leo´n, 1992). These occur at the juncture of the midribs and the main lateral veins, and apparently exude sugars. Whether there is regular ant association in Campyloneurum, as reported in some polypodiaceous ferns (Koptur et al., 1982), is unknown. Campyloneurum, including the two 1-pinnate species mentioned above (these excluded by Lellinger, 1988), is monophyletic and clearly allied to a large clade of other New World Polypodiaceae (Haufler, unpubl. data; Schneider et al., 2003), most especially to Niphidium and then to Microgramma. Nearly all species in this clade are simple-bladed. Species of Campyloneurum occupy an unusually wide variety of habitats, from sea level to above 4000 meters in paramo vegetation; species can be terrestrial, epipetric, or epiphytic.