Polystichum distans E.Fourn.

Authority

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

Family

Dryopteridaceae

Scientific Name

Polystichum distans E.Fourn.

Description

Species Description - Caudices 3–8 cm diam., infrequently collected because of their massive size; fronds mostly 50–150 cm long; stipes 10–30(–40) cm long, 3–6 mm diam., ca. 1/4 to nearly equaling the blade length; stipe bases with dense, ovate-lanceolate scales mostly 10–30 x 2–6(–8) mm, scales mostly blackish, lustrous, with very narrow brownish margins, or scales dark brown, margins denticulate to setose and with long, flaccid cilia, distally the stipes sometimes also copiously scaly; blades subcoriaceous, 25–65(–85) x 9–30(–35) cm, broadest at the bases or proximal 1–3 pairs of pinnae slightly reduced, attenuate at apices; rachises lacking buds, with lanceolate and hair-like scales mostly 3–6 mm long, denticulate or ciliate, a few scales often blackish or with a black central stripe; pinnae 1–2-pinnate, mostly 25–40 pairs, mostly 5–15(–18) x (1– )1.5–2(–2.5) cm, pinnules entire to crenate with a small acroscopic auricle, less often with larger pinnules shallowly to deeply pinnatifid at the bases, infrequently each with a ± free obovate lobe, both margins and tips spinulose and often slightly revolute; indument abaxially along costae, costules, and veins of lanceolate to fibrillose scales, the larger (broader) ones denticulate or spinulose; sori indusiate to exindusiate, often confluent at maturity, indusia tan to brownish, usually 0.3–0.8 mm diam., peltate, often fugacious; 2n=82 (Chis.).

Discussion

Type. Mexico. [Veracruz:] Orizaba, Schaffner 217a (not found at P or K).

Polystichum pallidum E. Fourn., Mexic. Pl. 1: 91. 1872, hom. illeg., non Gardner, 1842, nec Todaro, 1866. Type. Mexico. Oaxaca: Ghiesbreght s.n. (P; photo US!).

The differences between this species and P. rachichlaena are few and possibly not absolute, and it may be that the two should be considered variants of a single, polymorphic species. In general, P. distans has blacker, glossier, or darker-centered scales that run up the stipes for some distance. Polystichum distans also has more dissected pinnules that tend to be less rounded at tips, harsher blade texture, and generally smaller indusia (or indusia absent). All these characteristics vary considerably, especially in and around the Valle de Me´xico and in the western Sierra Madre Detailed morphometric, cytological, and isozymic work is needed to establish whether the differences are constant or not. Several collections from Veracruz (e.g., LaFrankie 1076, TEX; Narave F. 660, ENCB; Cochrane 8574, CAS, MEXU, UC; Zamora P-1034, UC) and Puebla are remarkable for their abundantly scaly stipes and rachises, very large dark brown to black scales to 3 x 0.8 cm, scales prominently spinulose at tips, 2- pinnate-pinnatifid to subtripinnate blades, and exindusiate sori. However, some collections more typical of P. distans, lacking the abundant large stipe scales, are also apparently exindusiate (e.g., Pringle 13638, from Hidalgo). Exindusiate collections seen are noted with an asterisk (*) in the citations. Mickel 3728 (UC), considered a hybrid between P. hartwegii and P. ordinatum by Mickel and Beitel (1988: 313), is typical P. distans; the spores and sporangia are well formed and appear normal. Some specimens of this species (e.g., Bartholomew 3359, UC; Ferna´ndez N. 509, IEB) have very large spores, and one suspects that they are polyploids. However, the only reported count for this species is diploid. Most collections from Hidalgo differ in their narrower, fewer, and less blackish stipe base scales; they also grow at lower elevations than typical for the species. The differences between these collections and specimens of P. hartwegii, often found at lower elevations than P. distans, from the same area are subtle and not altogether clear. Even more puzzling is the sole collection from Tamaulipas, from 1400 m; it has brown stipe base scales, and might with equal justification be called P. hartwegii. A specimen from Veracruz (Ventura A. 5037, XAL) is peculiar in having numerous (ca. 35) gall-like structures (viral or bacterial in origin?) produced from the receptacle. This number at ENCB lacks such galls (Barrington, in litt.). These are 2–5 mm diam., round in outline, flattened, solid (without noticeable cavities or insect larvae within), and about 1 mm thick. Remarkably, there is a single perfectly normal indusium borne in the center of each gall, and some abortive sporangia produced beneath the galls. The developmental processes that would allow normal indusia to be produced, while suppressing sporangial development cry out for explanation. A specimen of P. hartwegii from Morelos (Lyonnet 540900012, CAS) has some similar gall-like structures