Hymenophyllum subg. Mecodium

Kessler, Michael & Smith, Alan R., 2017, Prodromus of a fern flora for Bolivia. X. Hymenophyllaceae, Phytotaxa 328 (3), pp. 201-226 : 209

Key to the Bolivian species of Hymenophyllum subg. Mecodium

1 Blades extremely crisped, the margins strongly ruffled; blades mostly 0.75–2 cm wide, often indeterminate ..... H. fendlerianum

– Blades plane or with folded or undulate segments; blades to 10 cm wide, usually determinate ..................................................... 2

2 Involucres ± orbicular or broader than long, sometimes borne on a short, narrowly to broadly winged stalk ................................ 3

– Involucres suborbicular to deltate, lanceolate, or oblanceolate, attached by their width to the ultimate segments ......................... 5

3 Involucral margins erose to denticulate ................................................................................................................................ H. ferax

– Involucral margins entire .................................................................................................................................................................. 4

4 Rachises winged throughout, wings often extending onto petioles; blades 1–10 cm wide, lax to usually erect ............. H. axillare

– Rachises not winged in proximal 1/3–1/2 of the blades; blades 1–4 cm wide, lax, usually pendent ......................... H. undulatum

5 Involucral bases acute; receptacles often exserted ........................................................................................................................... 6

– Involucral bases obtuse to rounded; receptacles not exserted .......................................................................................................... 8

6 Leaves mostly 5–20 cm long; ultimate segments> 5 mm long ........................................................................... H. trichomanoides

– Leaves 1–4(6) cm long; ultimate segments <5 mm long ................................................................................................................. 7

7 Involucres broadest at or above their middle, as wide or wider than the ultimate segments, lacking lateral wings .. H. apiculatum

– Involucres broadest below middle, narrower than or equalling the ultimate segments in width, often with the segments extending laterally on the involucres to form wings .................................................................................................................... H. brevistipes

8 Involucres lacerate to repand at apices; blades rhombic to lanceolate, usually gradually tapered at base ................... H. lehmannii

– Involucres entire or nearly so at apices; blades ovate to lanceolate, not gradually tapered at base ................................................. 9

9 Petioles not winged (often basal rachises not winged either); leaves usually 12–30 cm long; 2100–3200 m ............. H. mathewsii

– Petioles at least partly winged; leaves usually <15 cm long; 100–2100(–2400) m .................................................... H. polyanthos