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Rhizocarpon viridiatrum (Wulfen) Körber

Synonyms:

Family: RHIZOCARPACEAE

Habitat: Ubiquitous

Description

    Thallus at first parasite, lichenicolous becoming free and crustose (but always close to its host), made of areoles, rounded to slightly angular, separate by thin cracks, 0.5-1.5 mm diam., slightly convex becoming bulging, smooth, yellow, lemon, yellow-green, faint yellow, prothallus absent, thallus spreading laterally, leaving from place to place black necrotic spots, finally gives rise to free thallus with a black prothallus, of which the development stays limited as for non-parasitic similar species. Apothecia usually numerous, rounded to sligthly angular, 0.4-1 mm diam., disc slightly convex to convex, little or not protruding, in frame with the areole surface curve, disc black, not powdery, exciple inconspicuous except sometimes when young. Ascospores brown-blackish, broadly ellipsoid, submuriform, 17-32 x 10-16 µm. Photobiont: Chlorococcoid. Medulla: C-, K+/- yellow, Pd+/- orange, I-. Rather rare in our prospection area, on weakly acid rocks, notably schists, may additionally come with its host on granite rocks. Initially parasite of crustose lichens: Aspicilia, Acarospora, Lecidea, etc. and possibly with Miriquidica deusta, often found together, but with a with a strong preference for Aspicilia caesiocinerea that it may completely  eliminate,  later, after the host destruction, may continue a free life and develop a black prothallus that makes it difficult to distinguish in the field from Rhizocarpon lecanorinum.  The latter has a more developed black prothallus, apothecia arranged towards the center of a cluster of areoles horseshoe-shaped, and larger ascospores.*







Rhizocarpon viridiatrum sur Aspicilia caesiocinerea Port-Manec'h 1
Bernard BOUFFINIER



Rhizocarpon viridiatrum sur Aspicilia caesiocinerea Port-Manec'h 2
Bernard BOUFFINIER



Rhizocarpon viridiatrum sur Aspicilia caesiocinerea Port-Manec'h 3
Bernard BOUFFINIER



Rhizocarpon viridiatrum avec Aspicilia caesiocinerea Commana 1
Joƫl QUERELLOU



Rhizocarpon viridiatrum avec Aspicilia caesiocinerea Commana 2
Joƫl QUERELLOU



Rhizocarpon viridiatrum Bastia Corse
Bernard BOUFFINIER



Rhizocarpon viridiatrum sur Aspicilia caesiocinerea avec Miriquidica deusta Saint-Cadou
Serge HIBERT



Rhizocarpon viridiatrum avec Aspicilia caesiocinerea Commana 3
Joƫl QUERELLOU



Rhizocarpon viridiatrum avec Aspicilia caesiocinerea Commana 4
Joƫl QUERELLOU



Rhizocarpon viridiatrum avec Aspicilia caesiocinerea Commana 5
Joƫl QUERELLOU



Rhizocarpon viridiatrum Groix 1
Hans TOETENEL



Rhizocarpon viridiatrum Groix 2
Hans TOETENEL



Rhizocarpon viridiatrum Groix 3
Hans TOETENEL



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