Polypodium robertianum Hoffm.
Dryopteris robertiana (Hoffm.) C.Chr.
Polypodium calcareum Sm.
Dryopteris disjuncta (Rupr.) C.V.Morton

Limestone oak fern, Robert's oak fern, Northern oak fern.

Rhizome long-creeping, dark brown or black, forking. Fronds 40 x 15 cm, deciduous, monomorphic, blade/stipe ratio: 3:2 to 2:1. Stipe grooved, dull green, scaly at the base, soon falling. Lamina 2-pinnate-pinnatifid, triangular in outline, stiff, dull surface, very glandular, especially on the lower surface and the rhachis. Pinnae 9 to 12 pair, lowest pair similar in form (not size) to the next pair; pinnules lower basal pinnule of the lowest pinnae cut like adjacent pinnules , costae grooved above, continuous from rhachis to costae, margins entire to slightly crenate; veins free, simple or forked. Sori round, closer to the margin, on both edges of the segments; indusium absent.

Calcareous woodlands or swamps.

Algeria, Libya.

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