Abrodictyum, C. Presl, 1843

Dubuisson, Jean-Yves, Bauret, Lucie, Grall, Aurelie, Senterre, Bruno, Said, Ahamada H., Pynee, Kersley, Ebihara, Atsushi & Hennequin, Sabine, 2017, Taxonomic study of the fern genera Abrodictyum C. Presl and Trichomanes L. (Hymenophyllaceae, Polypodiidae) in the western Indian Ocean, and description of a new Abrodictyum species for Madagascar, Phytotaxa 327 (3), pp. 201-222 : 207

Key for Abrodictyum and Trichomanes species in the western Indian Ocean

1. Fronds simply pinnate, with pinnae lobed ......................................................................................................... T. madagascariense

- Fronds more than simply pinnate ..................................................................................................................................................... 2

2. Distal ultimate lobes or segment always single-veined, free ........................................................................................................... 5

- Distal ultimate lobes or segment usually multi-veined and/or fused ............................................................................................... 3

3. Pinnules lobed, toothed margin .......................................................................................................................................... T. boivinii

- Pinnules pinnatifid to bi-pinnatifid, entire margin ........................................................................................................................... 4

4. Pinnules usually bi-pinnatifid; ultimate segments fused at least at their third length, mostly with capillary apices; endemic to Seychelles........................................................................................................................................................................ T. cupressoides

- Pinnules pinnatifid to lobed, spatulate with proximal ultimate segments linear and entire, and distal ultimate segments fused; endemic to Madagascar........................................................................................................................................... A. pachyphlebium .

5. Lamina apparently absent or reduced to one row of cells on both sides of the veins ...................................................................... 6

- Lamina always developed. ................................................................................................................................................................ 7

6. Fronds sub-sessile or with short stipes not exceeding 4–5 cm, narrowly oblong to linear on herbarium, always with a narrowly cylindrical brush-like shape in situ ............................................................................................................... A. cylindratum sp. nov.

- Fronds with stipes usually longer than 4–5 cm, narrowly to widely lanceolate on herbarium, plane or with a lanceolate brush-like shape in situ ............................................................................................................................................ A. parviflorum comb. nov.

7. Lamina of ultimate segments usually not exceeding 3 cells on both sides of the veins .................................................................... 8

- Lamina of ultimate segments usually more than 3 cells on both sides of the veins ......................................................................... 9

8. Lamina width often variable within the same frond; fronds narrowly to widely lanceolate, plane or with a brush-like shape; usually more than 6 sori per pinna ...................................................................................................................... A. parviflorum comb. nov.

- Lamina width usually not variable within the same frond; fronds linear to narrowly oblong, sometimes narrowly lanceolate but never widely lanceolate, always plane; often a single sorus per pinna, rarely more than 6 sori per pinna.......................................... ........................................................................................................................................................................ A. angustimarginatum

9. Rhizomes erect; lamina without a distinct marginal row of cells ................................................................................................... 10

- Rhizomes short-creeping; lamina with a distinct marginal row of cells .............................................................. A. tamarisciforme

10. Fronds never more than bi-pinnate-pinnatifid, often curled in the wild; sori obconic to campanulate, with a slightly to well dilated mouth ............................................................................................................................................................................... A. franceae

- Fronds bi-pinnate pinnatifid to tri-pinnate-pinnatifid, never curled in the wild; sori cylindrical, truncated to slightly bilabiate with a slightly dilated mouth ........................................................................................................................................ A. pseudorigidum