Hymenophyllum subg. Sphaerocionium

Kessler, Michael & Smith, Alan R., 2017, Prodromus of a fern flora for Bolivia. X. Hymenophyllaceae, Phytotaxa 328 (3), pp. 201-226 : 211-212

Key to the Bolivian species of Hymenophyllum subg. Sphaerocionium

1 Blades bearing hairs on both margins and surfaces .......................................................................................................................... 2

– Blades bearing hairs only on margins and often veins, the surfaces between the veins glabrous .................................................. 14

2 Veins with wings perpendicular to the plane of the blade on one or both blade sides ..................................................................... 3

– Veins unwinged on both blade sides ................................................................................................................................................. 5

3 Rachises unwinged throughout .................................................................................................................................... H. plumosum

– Rachises winged ............................................................................................................................................................................... 4

4 Pinnae linear-lanceolate, 2.5–3.7 × 0.7–1 cm, with (6)7–12 segment pairs ............................................................ H. pyramidatum

– Pinnae ovate to ovate-lanceolate, to 2.5 × 0.8 cm, with 3–6(8) segment pairs ........................................................ H. verecundum

5 Petioles filiform, 0.15–0.25 mm in diameter .................................................................................................................................... 6

– Petioles stout, 0.4–0.6 mm in diameter .......................................................................................................................................... 10

6 Rachises unwinged ........................................................................................................................................................................... 7

– Rachises winged, nearly or entirely to the blade base ...................................................................................................................... 8

7 Fronds 20–100 cm long; blades pinnate-pinnatifid to 2-pinnate-pinnatifid; hairs dense, obscuring laminar tissue (both sides) ....... .......................................................................................................................................................................................... H. amabile

– Fronds 10–20 cm long; blades pinnate-pinnatifid; hairs relatively sparse, not obscuring laminar tissue ...................... H. jimenezii

8 Petiolar hairs simple, 2- or 3-celled, rarely forked ......................................................................................................... H. tegularis

– Petiolar hairs mostly stellate, a few only forked .............................................................................................................................. 9

9 Blades to 11 mm wide, 5–20 times as long as wide, with 15–40 pinna pairs .............................................................. H. angustum

– Blades 10–25 mm wide, 2–7 times as long as wide, with 4–20 pinna pairs ...................................................................... H. fragile

10 Rachises unwinged; blades densely hairy ...................................................................................................................................... 11

– Rachises at least partly winged; blades moderately hairy .............................................................................................................. 13

11 Blades very densely hairy, the hairs matted, appressed, completely obscuring the blade surface; pinnae apically acuminate .......... ...................................................................................................................................................................................... H. speciosum

– Blades densely hairy, the hairs loosely arranged; pinnae apically rounded ................................................................................... 12

12 Hairs on pinnae stalked-stellate or stalked-bistellate ...................................................................................................... H. amabile

– Hairs on pinnae simple or stalked-stellate ........................................................................................................................ H. apteryx

13 Marginal hairs sessile; rachises fully winged; fertile pinnae usually contiguous ............................................................ H. plumieri

– Marginal hairs stalked; rachises not winged toward the base; groups of fertile pinnae often interrupted by a few sterile ones ........ .................................................................................................................................................................................... H. interruptum

14 Petioles filiform, <0.3 mm in diameter, <5 cm long ...................................................................................................................... 15

– Petioles stout,> 0.3 mm in diameter, usually> 5 cm long .............................................................................................................. 20

15 Rachises unwinged at base ............................................................................................................................................................. 16

– Rachises winged to base ................................................................................................................................................................. 18

16 Leaves hemidimorphic, with proximal pinnae fertile and distal pinnae sterile; rachises, costae, and margins with simple hairs; leaves to 36 cm long .......................................................................................................................................... H. hemidimorphum

– Leaves monomorphic; rachises, costae, and margins with forked or stellate hairs; leaves to ca. 20 cm long ............................... 17

17 All pinnae at least slightly adnate and often decurrent on rachises; marginal hairs lacking dark bases, some of them stalked ......... ........................................................................................................................................................................................... H. elegans

– Proximal and often also distal pinnae stalked; marginal hairs with dark bases, all subsessile ............................. H. trichophyllum

18 Marginal hairs mostly simple or forked at bases; segment margins undulate ................................................................. H. crispum

– Marginal hairs of segments mostly stellate, bistellate, or twice-forked; segments flat .................................................................. 19

19 Pinnae subentire to apically bifid ................................................................................................................................... H. capurroi

– Pinnae more divided ...................................................................................................................................................... H. hirsutum

20 Rachises not winged to base ........................................................................................................................................................... 21

– Rachises winged to base ................................................................................................................................................................. 23

21 Veins adaxially glabrous, abaxially mostly with simple or basally forked hairs ................................................. H. aff. subrigidum

– Veins on both blade sides with hairs, hairs adaxially at least partly stellate .................................................................................. 22

22 Lower pinnae subpetiolulate, tripinnatifid or almost completely bipinnate at bases; blades 9–17 cm wide; primary pinnae with 9–12 pairs of pinnules; petioles 0.7–1.6 mm in diameter ............................................................................................ H. ruizianum

– Lower pinnae slightly adnate, bipinnatifid; blades 2–6 cm wide; primary pinnae with 4–7 pairs of pinnules; petioles <0.6 mm in diameter ..................................................................................................................................................................... H. trapezoidale

23 Segments and rachis wings slightly to strongly undulate; petioles lacking stellate hairs among the simple and forked ones ........... ........................................................................................................................................................................................ H. valvatum

– Segments flat, rachis wings flat to undulate; petioles with mixed simple, forked, and stellate hairs ............................................ 24

24 Marginal hairs mostly forked (some simple) .............................................................................................................. H. platylobum

– Marginal hairs simple ..................................................................................................................................................................... 25

25 Involucres broader than long, with hairy margins; rachis wings wavy ......................................................................... H. latisorum

– Involucres longer than broad, without or with very few, scattered hairs; rachis wings flat ................................... H. microcarpum