Thursday, April 7, 2016

Placopsis Gelida, Bullseye!


Day 177: Many crustose lichens are easy to overlook. At a glance, they might appear to be an inclusion in a rock face or a mineral deposit on the surface. For example, this specimen of Placopsis gelida (a "bullseye" lichen, ref. Vitt et al) could have been mistaken for a discoloured bit of quartz in a darker matrix when seen from a distance. Up close, the lichen reveals its complex form, brown cephalodia (wart-like structures) dotting the pale green thallus and darker lobes extending like fingers along its margins. Crustose lichens adhere tightly to their substrate material; it would be difficult to lift one of those tiny projections even with a pocket knife.

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