On canyon walls visible within 2 meters of water at any level in recent years. What appear to be old growth areas show as bleached rocks and can be most anywhere on canyon walls. Circles are from 2cm-25cm diameter and ones which appear to be most “alive” are as much as 4cm thick. One shown here has a plant growing in it, not uncommon in larger circles. Very crusty – Lichen or Mineral?
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The first two photos are a moss. There are several that grow on dry bare rock, e.g., Grimmia, with abundant and conspicuous terminal setae giving it a grayish, grizzled appearance like this.
The third photo, the one with the big black dots, is a crustose lichen, perhaps Sarcogyne. Notice that the black disks — apothecia — have split margins, this is common in Sarcogyne. Someone just told me that Lecidea tessellata also does this. Maybe Porpidia does sometimes, too? You would really need to dissect one of the apothecia to check the anatomy and spore characteristics to be sure.
The final two photos, the ones showing just ghostly white disks on the rock, could well be a discoloration under a moss that’s been washed (indeed, scoured!) off the rock. But it looks entirely too perfect, so I’d suggest that it’s most likely another lichen, a sterile crustose one. It’s really hard to get anywhere with these things without doing spot tests and getting good close-up shots showing full detail of any structures on the thallus (like soralia, for instance). I see little “warts”, but the bare rock itself has wart-like irregularities, too, so who knows if that’s part of the lichen or not. If you had a sample, you could scratch into it to see if it has a layer of algae, and you could check directly if the warts are part of the lichen or the rock.
Created: 2013-04-13 02:06:36 AST (+0300)
Last modified: 2015-05-28 23:00:20 AST (+0300)
Viewed: 28 times, last viewed: 2017-07-29 04:35:04 AST (+0300)