Bacidia is a genus of lichen-forming fungi in the family Ramalinaceae. These lichens are characterised by their crustose growth form, distinctive club-shaped reproductive structures called apothecia that contain long, needle-like spores, and their symbiotic partnership with green algae. Bacidia species typically grow on various substrates including tree bark, rock surfaces, and occasionally soil, and are distinguished from related genera by their specific spore characteristics and internal structures.

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