Didymoglossum

Kessler, Michael & Smith, Alan R., 2017, Prodromus of a fern flora for Bolivia. X. Hymenophyllaceae, Phytotaxa 328 (3), pp. 201-226 : 204-205

Key to the Bolivian species of Didymoglossum

1 Blade margins with minute scales ...................................................................................................................... D. membranaceum

– Blade margins hairy or glabrous, lacking scales .............................................................................................................................. 2

2 Blades without marginal hairs and with distinct submarginal veins; sori wholly immersed, without lips and not dark-edged ......... ................................................................................................................................................................................. D. kapplerianum

– Blades with marginal hairs and without submarginal false veins; sori usually with 2 distinct, dark-edged lips ............................. 3

3 Venation flabellate, blades lacking a midvein or with midvein not extending beyond the middle of the blade .............................. 4

– Venation pinnate, blades with a distinct midvein ............................................................................................................................. 6

4 Leaves 3–8 mm long; fertile blades each usually with a single terminal sorus; blade tissue very thin and translucent ...... D. ovale

– Leaves> 10 mm long; fertile blades usually with several sori; blade tissue firm-herbaceous ......................................................... 5

5 Marginal hairs simple or bifid; veins not so crowded (often>12 rows of cells between adjacent veins) ................. D. hymenoides

– Marginal hairs stellate; veins and veinlets crowded (not more than 5 rows of cells between adjacent veins) ........... D. punctatum

6 Blades entire or irregularly lobed distally; stellate hairs present along the ± entire margins ........................................................... 7

– Blades pinnatifid to 2-pinnate-pinnatifid; stellate hairs mainly in the sinuses, bifid hairs elsewhere on the margins ..................... 8

7 Leaves 5–17 × 1–3 mm; lips of the sori each with a single row of dark cells; sori immersed to the lips ................ D. angustifrons

– Leaves 3–8 × 2–6 mm; lips of the sori each with several rows of dark cells; sori partly exserted ...................................... D. ovale

8 Sori immersed or nearly so; nearly all false veins not connected, partly parallel to the blade margins ............................ D. krausii

– Sori exserted; false veins few, unconnected usually not parallel to the blade margins .................................................................... 9

9 Lips of involucres mostly broader than long; laminar cells mostly isodiametric; false veins sparse, scattered ....... D. hymenoides

– Lips of involucres mostly as long as or longer than broad; laminar cells mostly elongate; false veins usually abundant ................. ............................................................................................................................................................................................ D. reptans