Crustose Lichens
Are Lichens attached tightly to substrate without a lower Cortex – The Lichen cannot be separated from the substrate it’s growing on.

Mycoblastus sanguinarioides
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Rhizocarpon lecanorinum
Are Lichens attached tightly to substrate without a lower Cortex – The Lichen cannot be separated from the substrate it’s growing on.
Mycoblastus sanguinarioides
…
Rhizocarpon lecanorinum
On Spruce Bark
On Inter-tidal Boulders
On Oak Bark
On Oak bark