Abrodictyum, C. Presl

Dubuisson, Jean-Yves, Bauret, Lucie, Boucheron-Dubuisson, Elodie & Rouhan, Germinal, 2022, Abrodictyum inexpectatum, an unexpected new fern species (Hymenophyllaceae, Polypodiidae) for Madagascar, as revealed by an integrative approach, Phytotaxa 568 (1), pp. 83-91 : 90

New key to the Abrodictyum species in the Afro-Malagasy region (modified from Dubuisson et al. 2017)

- Distal ultimate lobes or segment usually multi-veined and/or fused, often spatulate and appearing serrulate...... A. pachyphlebium

1. Distal ultimate lobes or segment usually single-veined, free, or sometimes fused by pair................................................................ 2

2. Lamina apparently absent or reduced to one row of cells on both sides of the veins ........................................................................ 3

- Lamina always developed .................................................................................................................................................................. 4

3. Fronds subsessile or with short stipes not exceeding 4–5 cm, narrowly oblong to linear on herbarium, always with a narrowly cylindrical brush-like shape when fresh ...................................................................................................................... A. cylindratum

- Fronds with stipes usually longer than 4–5 cm, narrowly to widely lanceolate when dried, plane or with a lanceolate brush-like shape when fresh ......................................................................................................................................................... A. parviflorum

4. Lamina of ultimate segments usually not exceeding 3 cells on both sides of the veins..................................................................... 5

- Lamina of ultimate segments with usually more than 3 cells on both sides of the veins................................................................... 6

5. Lamina width often variable (1 to 3 rows of cells on both sides of the veins) 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

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

6. Rhizomes erect; lamina without a clearly distinct marginal row of cells; plants usually terrestrial or saxicolous, rarely epiphytic... ............................................................................................................................................................................................................ 7

- Rhizomes short-creeping; lamina with a clearly distinct marginal row of cells; plants usually epiphytic, sometimes saxicolous ..... ................................................................................................................................................................................ A. tamarisciforme

7. Fronds bipinnate-pinnatifid or more divided, always plane in the wild, never crispate or curled ..................................................... 8

- Fronds rarely more than bipinnate-pinnatifid, usually with pinnules curled in the wild .................................................. A. franceae

8. Fronds often more divided than bipinnate-pinnatifid, broadly lanceolate to triangular, often exceeding 30 cm long; lamina dark green and opaque; sori cylindrical to slightly campanulate .................................................................................................. A. dregei

- Fronds usually not more divided than bipinnate-pinnatifid, usually not exceeding 13.5 cm long, narrowly lanceolate; lamina light green and translucent; sori obconic (cup-shaped) ....................................................................................... A. inexpectatum sp. nov.