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Collema nigrescens (Huds.) DC

Synonyms:

Family: COLLEMATACEAE

Habitat: Oceanic zone

Description

   Thallus foliose, more or less pleated, up to 10 cm diam., broad lobes up to 1 cm wide, ribbed and densely covered with smooth pustulous bubbles (toad's skin-like), dark brown-olive, blackish if dry, green-bottle or green-olive when moist. On upper surface, notably towards the center, minute blackish nodular-granular isidia, to 0.2 mm diam., are sometimes present. Apothecia usually very numerous, often covering most of the thallus, 0.4-1 mm wide, disc flat or slightly convex, pale brown-pink to dark brown, sometimes pruinose, white, with a narrow, at times isidiate, thalline exciple. Ascospores needle-shaped, 5-12-septate. 50-90 x 3-4,5 µm. Photobiont : Nostoc. Chemical spot tests negative. This species has strong coastal and oceanic trends and is found at the basis of trees and in cracks of rocks and walls (notably those of parish enclosures near the sea). N.B. Collema subnigrescens has no isidia and ascospores are smaller.*







Collema nigrescens Crozon 1
Bernard BOUFFINIER



Collema nigrescens Dinéault 1
Bernard BOUFFINIER



Collema nigrescens Crozon 3
Bernard BOUFFINIER



Collema nigrescens Crozon 4
Bernard BOUFFINIER



Collema nigrescens avec Nephroma laevigatum Crozon 5
Michel DAVID



Collema nigrescens Dinéault 2
Bernard BOUFFINIER



Collema nigrescens Dinéault 3
Bernard BOUFFINIER



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