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Verrucaria nigrescens  Pers. var. nigrescens f. nigrescens

Synonyms:

Family: VERRUCARIACEAE

Habitat: Ubiquitous

Description

    Thallus crustose, rather thick but superficial, cracked, areolate, areoles smooth, flat to slightly convex, angular with black edges, 0.2-0.8 mm, smooth to rough, brown-black, blackish, blackish slighly tinged with green when moist, colours more or less drab and not glossy, incompletely green when moist, margin well developed, distinct, prothallus absent. One or several perithecia per areole,  1/2 to 1/3 immersed in thallus and therefore little protruding, small, 0.2-0.5 mm diam., black. Ascospores simple, broadly ellipsoid, 19-26 x 11-13 µm. Chemical spot tests negative. Not especially maritime, common on calcareous rocks and occasionally on mortar of walls or concrete. See Verrucaria macrostoma of which the areoles and perithecia are bigger and markedly turning green when moist and, Verrucaria viridula more brown-greenish and less blackish, appearing less areolate owing to a less visible prothallus, and with less protruding perithecia. See also Verrucaria fusconigrescens  that grows on siliceous rocks on the foreshore and has a more shiny thallus and Hydropunctaria maura that also thrives on the foreshore but is much blacker with broad and flat perithecia. N.B. An isidiate form (or blastidiate according to some authors) has been described: see Verrucaria nigrescens var. nigrescens f. tectorum that is easily confused with Verrucaria macrostoma f. furfuracea which is sorediate and markedly greener when moist. N.B. Verrucaria nigrescens s.l. is highly variable and probably encompasses several taxa.







Verrucaria nigrescens Pointe de l'Armorique sur calcaire 1
Alain GERAULT



Verrucaria nigrescens Le Passage 2
Alain GERAULT



Verrucaria nigrescens Caen sur calcaire avec Caloplaca flavescens
Alain GERAULT



Verrucaria nigrescens L'Aber Four à chaux 1
Michel DAVID



Verrucaria nigrescens Aber Four à chaux 2
Michel DAVID



Verrucaria nigrescens Ile d'Aix
Joël QUERELLOU



Verrucaria nigrescens Durtal
Joël QUERELLOU



Verrucaria nigrescens Durtal 2
Joël QUERELLOU



Verrucaria nigrescens Ardenne 1
Jacques HAINE



Verrucaria nigrescens Asques Ardenne 2
Jacques HAINE



Verrucaria nigrescens Ile du Levant 1
Michel DAVID



Verrucaria nigrescens Ile du Levant 2
Michel DAVID



Verrucaria nigrescens Ile du Levant 3
Michel DAVID



Verrucaria nigrescens Ile du Levant 4
Michel DAVID



Verrucaria nigrescens Le Passage 3
Alain GERAULT



Verrucaria nigrescens Habitat sur ciment Le Passage 1
Alain GERAULT



Verrucaria nigrescens Aber Four à chaux 3
Michel DAVID



Verrucaria nigrescens Aber Four à chaux 4
Michel DAVID



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