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Polypodium European Group

P. interjectum is the hybrid cross of P. cambricum and P. vulgare. Note particularly: the shape of the frond, the presence/absence of paraphyses (translucent, glandular branching structures within the sorus; hand lens required), and phenology, specifically, frond emergence. Given maturity and amenable habitat, P. interjectum, possessing hybrid vigor, is larger than the others. Paraphyses in P. cambricum is conclusive for that species.

Species Rhizome Indument Blade Height To Blade Form Sporangia Dimensionality Phenology Habitat Distribution
cambricum scales lanceolate, red-brown, to 16 mm 30 cm small fronds triangular, larger ones broadly oval early green, later yellow; paraphyses present lowest pinnae sharply inflexed above the plane of the blade emerges August-September on calcareous rock, mortared walls, sometimes epiphytic on oaks, often coastal westernmost and southern Europe, northern Africa, east to Lebanon
interjectum scales lanceolate, abruptly narrowed above a dilated base, to 11 mm 50 cm narrowly oval, truncated base, arching early green, later yellow, then rusty brown; paraphyses absent lower pinnae, particularly the lowest pair, bend above the plane of the blade (less so than with P. cambricum) fronds emerge in June-July, develop over a four week period neutral to basic rocks, walls, well-drained sites Portugal to Scotland, east to central Europe
vulgare scales lanceolate, pale brown, less than 5 mm long 25 cm lanceolate to linear, parallel sides in the lower half, truncated base early green, later yellow, then rusty brown; paraphyses absent lowest pinnae pair only slightly bending forward, down; pinnae rolling up into the rachis (above the plane) when desiccated fronds emerge in early May, develop over a four week period acidic, well-drained locations, on rocks, logs, hillsides central and northern Europe, less common southern Europe, eastern Asia

Characters listed were chosen for their value in distinguishing between species.

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