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.

Images

21410
magnification 30x
21409
magnification 10x
21411
perithecial section, in water, at 100x
21412
perithecial section, in water, at 100x
21413
perithecial section, in KOH, at 100x
21414
perithecial section, in K/I, at 100x
21415
perithecial section, in water, at 400x
21416
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 01:35:15 CDT (-0400)
Last modified: 2008-09-14 01:35:15 CDT (-0400)
Viewed: 44 times, last viewed: 2016-11-19 09:18:22 CST (-0500)