Diplazium exindusiatum M. Kessler & A.R.Sm., 2018

Kessler, Michael & Smith, Alan R., 2018, Prodromus of a fern flora for Bolivia. XXXII. Athyriaceae, Phytotaxa 334 (2), pp. 141-151 : 146

Diplazium exindusiatum M. Kessler & A.R.Sm. , sp. nov. ( Fig. 1 )

Notable for its densely scaly stipes, rachises, costae, costules, and ultimate axes of ultimate segments and exindusiate sori, the latter a rare condition in neotropical Diplazium .

Type.— BOLIVIA. Cochabamba: Tiraque, El Limbo, ceja de monte, mesobosque hiperhúmedo caracterizado por Freziera karsteniana (Szyszy ł.) Kobuski y Brunellia boliviana E.Britton ex Rusby , 17°09’37S, 65°38’32W, 2920 m, 15 Feb 2005, M. Alem et al. 199 (holotype UC; isotype BOLV not seen).

Plants terrestrial; rhizomes unknown; stipe base scales to 13 × 1.5–2.5 mm, lanceolate, spreading or a little deflexed distally, shiny brown, weakly clathrate, bearing marginal teeth to 0.5 mm, the largest teeth 2–3 cells wide at bases; petioles dark brown at bases, lighter brown distally, ca. 35 cm long, 1.2 cm diam. at bases, throughout with rather dense, lanceate scales to 1.3 cm long; blades to at least 40 cm long (middle portion not seen), probably approaching 50–60 cm long; blades chartaceous, bipinnate-pinnatifid, with at least 10 (probably ca. 15, complete fronds not seen) pairs of lateral free pinnae before the confluent, gradually tapered, pinnate-pinnatifid (ultimately pinnatifid) blade apex, proximal pinna pair the largest, to 22 × 11 cm, ovate; rachises light brown, with numerous conspicuous scales like those of petioles, but distally gradually becoming smaller; largest pinnae (proximal pair) stalked to 1.2 cm, subopposite, more distal pinnae alternate, shortened at the base, the basiscopic basal one on proximal pinna pair ca. half the length of the longest pinnules on the same pinna; largest pinnules (on proximal pinnae) to ca. 6 × 1.8 cm, deeply pinnatifid to ca. 1–2 mm from costules, segments to 6 mm wide from sinus to adjacent sinus, and 6 mm wide between adjacent costulets, slightly oblique, falcate towards tips, minutely denticulate at apices; veins to 7 pairs on ultimate segments, simple or sometimes forked near segment margins, lowermost pair from adjacent segments meeting margins above sinuses; costal scales numerous and conspicuous, like those of stipes and rachises but smaller, to 3 mm, marginally toothed; costules, costulets, and even ultimate veins, and margins with scales abaxially, also with small, uniseriate, light brownish segmented hairs (probably reduced scales); laminar tissue abaxially between veins lacking hairs and scales; laminae adaxially glabrous; smaller sori round nearly so, but larger ones on more developed pinnules oblong, to 2.5 mm long, with sporangia angling away from veins in both directions; indusia absent (no trace in mature sori); spores tan or light brown.

Range: —Endemic to Bolivia ( CO).

Ecology: —Rare (known only from the type); very wet, montane forests; 2920 m.

Notes: —Nearest affinities are uncertain. This is one of the few species of Diplazium in the Neotropics completely lacking indusia. Diplazium lindbergii (Mett.) Christ , widespread in the Neotropics, also often lacks indusia or has indusia reduced to very narrow remnants; it occurs in Bolivia but has less dissected, pinnate-pinnatifid blades, and much less scaly axes (stipes, rachises, costae). We surmise that it is not closely related to D. exindusiatum . Moreover, D. exindusiatum is not clearly related to any of the similarly dissected, larger, bipinnate-pinnatifid species we know in the Andes.

Figures

FIGURE 1. Diplazium exindusiatum. Holotype: M. Alem et al. 199.