Mickel, John T. & Smith, Alan R. 2004. The pteridophytes of Mexico. Mem. New York Bot. Gard. 88: 1-1054.
Dryopteridaceae
Genus Description - Terrestrial; rhizomes mostly suberect to erect, sometimes short-creeping, scaly, with old stipe bases and roots frequently forming stout caudices to 4 cm diam.; fronds small to mediumsized to large, usually clumped; blades herbaceous to chartaceous, pinnate-pinnatifid to quadripinnate or more divided; midribs, especially the adaxial rachises, costae, and costules, with short, reddish to red-brown, jointed hairs (ctenitoid hairs) 0.2–0.8 mm long; rachises and costae abaxially with few to many scales, often these often inrolled, sometimes clathrate, flat or plane, also often with glands and jointed hairs; veins free, simple or forking in the ultimate segments; sori abaxial, round, indusia reniform, attached at sinuses, sometimes greatly reduced or even absent altogether; spores bilateral, spinulose; x=41.
Type: Ctenitis distans (Brack.) Ching [= Aspidium ctenitis Link]
Ctenitis is a genus of about 150 species, about evenly distributed between the Old and New World wet tropics, mostly of low and middle elevations. It has usually been thought to be related to the tectarioid ferns and perhaps allied to Tectaria and Lastreopsis. However, unpublished molecular data indicate that this relationship may not be as close as once thought (Hasebe et al., 1995; Cranfill, unpubl. data); rather, Ctenitis may be more intimately related to the dryopteroid clade (rather than the tectarioid clade). Twenty-one species of Ctenitis are known from Mexico, most of them restricted to only the southernmost part of the country. Apparently, southern Mexico and Guatemala, especially in calcareous habitats, are a major center of diversity for the genus in the Neotropics. Almost all species of Ctenitis have distinctive jointed hairs on the blades, especially on the adaxial rachises, costae, and minor axes. These hairs are usually short, less than 0.5 mm long and often much shorter than that, with very short cells and reddish joints. This kind of hair, often called a ctenitoid hair, is named for the genus, and is an easy character to use in distinguishing Ctenitis from most other genera of ferns, particularly Dryopteris and Thelypteris, with which Ctenitis has historically been combined and confused. Similar hairs are found in Tectaria.