Observation 11098: Verrucaria macrostoma Dufour ex DC.
When: 2008-06-08
Herbarium specimen reported

Notes: crust lichen, on exposed sandstone
THALLUS: areolate to subsquamulose, areoles mostly 0.5-1.0 mm, surface smooth and dark brown, basally pinched and developing lateral and some lower cortex, cortex composed of tightly-packed round cells with brown pigment caps, covered with thin hyaline layer of dead cells (POL+ white), K- or lower cortex K+ weak red-violet
MEDULLA: white
ALGAE: green, in a continuous dense layer just below well-defined cortex, K-
APOTHECIA: perithecia, almost completely immersed, visible as barely-raised black pimples, subglobose, exciple pale brown and uniform, involucrellum black and clasping exciple on top third to half, periphyses mostly dissolving, hymenial gel K/I+ blue, asci K/I- and broadly clavate
SPORES: 8 per ascus, biseriate, elliptical, smooth outside but with texture and usually one large bubble inside, (13)17+/-1.5(19) x (8.4)11+/-2.5(15) µm (Q=(1.1)1.5+/-0.3(2.1)) (N=11), K/I+ golden to red-brown

I’m positive of the genus, since there are no other crustose perithecioid genera with K/I+ hymenium and black involucrella, and 8-spored asci. V. macrostoma is very close, but spores are too small, and no Verrucaria mentions the K+ reaction of the lower cortex.


magnification 30x
magnification 10x
perithecial section, in water, at 100x
perithecial section, in water, at 100x
perithecial section, in KOH, at 100x
perithecial section, in K/I, at 100x
perithecial section, in water, at 400x
spores, in K/I, at 1000x

Proposed Names

58% (1)
Eye3 Eyes3
Used references: Nash’s Sonoran Flora
Based on microscopic features

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Eye3 = Observer’s choice
Eyes3 = Current consensus


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Created: 2008-09-14 00:35:15 CDT (-0500)
Last modified: 2008-09-14 00:35:15 CDT (-0500)
Viewed: 41 times, last viewed: 2016-10-24 09:54:21 CDT (-0500)