The days of collecting and pinning out nature to create pretty drawing room displays are far gone. Specimens, in any area and not just lichens, should only be collected to study for identification purposes. Lichens can be difficult to identify in the field, particularly crustose forms. Beginners will also initially struggle with the foliose and fruticose forms, but as identification skills improve there will be less of a need for collecting.
Use can be made of a herbarium. The Botanic Gardens in Glasnevin, Dublin has a large herbarium of lichens and fungi and this can be used by any serious learning lichenologist.
Ref: Fox HF. 2001. Lichen herbarium resources in Ireland . In Rushton BS, Hackney P & Tyrie CR, eds. Biological Collections & Biodiversity. Linnean Society, Systematics Association and Ulster Museum, Belfast . pp 55-68.