Mertensia bifida Willd., Kongl. Vetensk. Acad. Nya Handl. 25: 168. 1804.
Gleichenia bifida (Willd.) Spreng., Syst. Veg. 4: 27. 1827. Dicranopteris bifida (Willd.) Maxon, N. Amer. Fl. 16: 60. 1909. Type. Venezuela, Distrito Federal, Caracas, Bredemeyer s.n. (holotype, B, Willd. 19468).
Mertensia pubescens Humb. & Bonpl. ex Willd., Sp. Pl. ed 4,5: 73. 1810. Gleichenia pubescens (Humb. & Bonpl. ex Willd.) Kunth in H.B.K., Nov. Gen. Sp. Pl. 1: 29.
1816. Dicranopteris pubescens (Humb. & Bonpl. ex Willd.) Conz., Fl. Taxon.
Mexic. 1: 129. 1939. Sticherus pubescens (Humb. & Bonpl. ex Willd.) Nakai, Bull.
Natl. Sci. Mus. 29: 25. 1950. Type. Venezuela, Sucre, Cunamá, Santa Cruz, Humboldt & Bonpland s.n. (holotype, B -Willd. 19467).
Plants medium-sized, slender. Rhizome 1.5-2.5(3) mm thick, dark brown to reddish brown, the scales deciduous, concentrated at bifurcations and at petiole bases,
linear-lanceolate, long-acuminate with 2 apical setae, 1-3 x 0.2-0.6 mm, the margins with short, thin setae, cell texture rigid, usually with hyaline bases dark brown. Petiole ca.
20-70 cm long and 1.6-4.5 mm thick, light-castaneous, stramineus, basally with scattered scales resembling those of the rhizome. Rachis 15-25 cm long between pinnae, subpaleaceus, aphlebiae absent. Fiddlehead (2.5)3-8 mm in diameter, densely scaly, the scales appressed, matted, whitish to pale orange. Bud small, appressed, the scales lanceolate with rounded bases, apically glandular or with short cilia, 1.5-4.6 x 0.4-0.6 mm, basally 15-25 cell rows wide, whitish to light orange, the margins with numerous, delicate, contorted cilia 1/7-1/4 x the scale length, cell texture grated, lax-hyaline, with rounded cells. Pinnae (25)35-50(70) cm long, 1- to 3-forked (often unequally), 1st (and sometimes 2nd) axis linear to narrowly lanceolate, shorter than the 2nd, 2.5-4(8) cm long and 1-2 mm thick, usually not pectinate or with scattered internal segments, last axis 10-30(50) cm long and ca. 1 mm thick,
pectinate-pinnatifid, 2-4(5) cm wide with segments, with 2-3 segments per cm, the proximal internal segments lacking on the first 1-2 cm, and the proximal external segments truncate; adaxially with mixed scales, one type triangular, 0.2-0.3 x 0.05-0.1 mm, the second type linear, 1.4-2 x 0.3-0.5 mm, both scale types deciduous with age, whitish to light orange (specially on young pinnae), cell texture grated lax-hyaline, the cells rectangular to irregular; abaxially the scales arranged laterally, lanceolate to ovate, (0.6)1.5-3 x (0.2)0.4-0.8 mm, basally up to 7 cell rows wide, whitish, the margins with delicate cilia 1/5 x the scale length, cell texture grated lax-hyaline with rectangular cells. Segments 1.5-3(4) cm long and 1.8-2(3) mm wide, linear from a dilatate bases, apically pointed, chartaceous, the margins narrowly revolute; adaxially glabrous; abaxially densely scaly, the scales covering 70-100%, arachnoid, 0.05-0.3 mm in diameter; veinlets thin, parallel, slightly raised; midvein scales triangular to rhomboid and occasionally linear, 0.2-0.4 x 0.1 mm, whitish to light orange, the margins with abundant cilia 1/2-1 x the scale length, cell texture grated lax-hyaline with irregular cells. Sori inframedial, nested within arachnoid scales, 15-38 pairs per segment, 3-4 sporangia per sorus.
Distribution and ecology. Widespread in mountains of Cuba, Trinidad and Tobago, Panama, Colombia, Venezuela, Guyana, Ecuador, Peru, Bolivia, and southeastern Brazil. Locally abundant in montane forests, clearings, and along roadsides, often
forming large, pure colonies but also mixed within other shrubby vegetation, at 150-800 m on the Caribbean Islands and 325-2300 m in the Andes.
Sticherus bifidus is one of the most commonly misapplied names in the genus. It has been used for almost any specimen with a scaly indument on the abaxial segment surface in most herbaria, and by, e.g., Tryon & Stolze (1989) and Moran (1995). Østergaard & Øllgaard (2001) in their treatment of the genus Sticherus for Ecuador already noted that “S. bifidus” comprised several distinct species and described S. aurantiacus and S. brevitomentosus as new species. I here further treat S. ferrugineus, S. fulvus, S. decurrens, and S. ovatus as separate species. As a result, the present concept of S. bifidus is much narrower than that of previous workers and includes not only fewer collections but also only a single synonym (versus four synonyms cited by Østergaard & Øllgaard (2001)). All these species form a group of closely related taxa that probably involves hybrid complexes. In fact, the variability of S. bifidus s. str. suggests that it may itself be of hybridogenic origin. This
hypothesis needs to be corroborated by cytotanomic and/or molecular studies.
Sticherus bifidus is recognized by the combination of the following
characters: the distal axes are linear to slightly lanceolate, aphlebiae are lacking, the proximal internal segments are lacking (the first segments are ca. 1-2 cm away from the bud), the indument is of a matted, whitish color, and the bud scales are gland-tipped. Further diagnostic characters are the lax, grated, hyaline, ciliate bud scales which have more rounded basal cells than, e.g., S. ferrugineus. S. bifidus completely lacks hardened, darkened cells in any scale type. In comparison, S. fulvus has shorter, bicolorous scales with darkened cells and has short, but distinct internal proximal segments. S. ferrugineus has aphlebiae, often strongly orange scales, and linear-lanceolata bud scales. S. decurrens has bud scales with darkened, twisted apices, and well-spaced segments on the 1st axis.
Maxon (1909, 1912) described a monstrous form of S. bifidus, collected by himself (Jamaica, Below New Haven Gap, 1500-1600 m, Mar 1920, Maxon 936, US) on Jamaica. It is strikingly distinct in the highly reduced segments, resulting in 3-5 mm wide, subentire to broadly crenate wings along the axes, rather than the
pinnatifid segments typical of S. bifidus. In all other characters, this collection is similar to S. bifidus. The monstrous specimens were found as a few plants amid a large population of S. bifidus.
A different monstruous form is represented by several pinnatifid specimens from St. Vincent (Smith & Smith 907, BM), Guadaloupe, (Herminier s.n., BM), and Trinidad (Tacarigua Ward, El Tucuche massif, 750 m, 7 Aug 1963, Jermy 2680, BM). They have pinnatifid segments, large pinnae that are up to 40 cm long and 10 cm wide, and slender, trimerous aphlebiae. These specimens may not belong to S.
bifidus but rather to closely related species such as S. pseudobifidus, S. subremotus, and/or S. interjectus, but their identification is difficult because several important characters are hard to evaluate on such monstrous specimens.