Observation 10444: Lecanora argopholis (Ach.) Ach.

crustose lichen, on exposed limestone
THALLUS: areolate with almost radiating lobes at margin, strongly convex areoles, pale yellow-green to yellow-gray to gray, K+y, KC-, C-
MEDULLA: white, K-, KC-, C-
APOTHECIA: lecanorine; disc black with red sheen in young ones, nearly plane; rim thick, smooth, even, thalline; epihymenium pale brown, filled with granules; hymenium clear; hypothecium clear; amphithecium with thick continuous algal layer, medulla and cortex filled with strongly POL+ white small granules/crystals (insoluble in K); paraphyses abundant relative to asci, most with one or two branches, clear; barely expanded at tips, strongly conglutinated but easily separating in K; asci with IKI+ blue tip and walls
SPORES: 8 per ascus, clear, simple, elliptical, around 10-14 × 5-7 µm, rather variable size

The distinctive yellow-green color which is remarkably K+y but KC- is apparently diagnostic. It is quite common on rock of all types in canyon country.

This particular sample is covered with spidery black threads from a parasite. I have no idea how to identify it even to genus, since I can’t find anything resembling a reproductive organ. This parasite (or ones just like it) are also common.

Species Lists


10x magnification
30x magnification
Apothecial section, in water, at 100×.
Apothecial section, in water, at 100x, in cross-polarized light.

Proposed Names

87% (1)
Used references: Nash’s Sonoran Flora
Based on microscopic features
Based on chemical features: K+ thallus

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= Observer’s choice
= Current consensus


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Created: 2008-09-05 16:59:37 EDT (-0400)
Last modified: 2008-09-05 16:59:37 EDT (-0400)
Viewed: 44 times, last viewed: 2019-03-24 10:20:08 EDT (-0400)