Hymenophyllum subg. Hymenophyllum

Kessler, Michael & Smith, Alan R., 2017, Prodromus of a fern flora for Bolivia. X. Hymenophyllaceae, Phytotaxa 328 (3), pp. 201-226 : 207

Key to the Bolivian species of Hymenophyllum subg. Hymenophyllum

1 Involucres in the plane of the blade; ultimate segments 1–2 mm wide; leaves 8–35 cm long ........................................................ 2

– Involucres at an angle to the blade plane; ultimate segments to 1 mm wide; leaves <8(10) cm long ............................................. 3

2 Veins with triangular, erect lamellae (may be hard to see!) perpendicular to the plane of the blade; involucres broader than long, with dentate margins ...................................................................................................................................................... H. cristatum

– Veins lacking lamellae out of the plane of the blade; involucres as long as broad to 3 times as long, with entire to dentate margins .......................................................................................................................................................................................... H. fucoides

3 Leaves <1 cm long, (sub)peltate; involucral margins entire ........................................................................................... H. herzogii

– Leaves> 1 cm long, pinnate; involucral margins entire or dentate ................................................................................................... 4

4 Veins and rachises lacking hairs or with very few, whitish hairs; involucral margins entire ......................................... H. peltatum

– Veins and rachises with scattered, reddish hairs; involucral margins undulate to dentate ............................................................... 5

5 Involucral margins undulate to shallowly dentate; ultimate segments 0.4–0.6 mm wide, ascending .......................... H. assurgens

– Involucral margins dentate; ultimate segments 0.7–0.9 mm wide, spreading ............................................................ H. cordobense