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Yes, good, growing on moss instead of directly on soil can definitely be significant for this genus.
The most important thing for this observation, is the dense woolly tomentum on the upper surface near the margins — that places this firmly in the canina group (includes P. canina, P. membranacea, P. praetextata, P. rufescens and several others not listed in the Bhutan checklist). (I don’t recognize P. cichoracea, P. dolichospora or P. pindarensis, though.)
Ignoring these three we have no information about… Notice that the margins are curved up without any abruptly downturned tips. This rules out P. canina. I just recently learned that P. praetextata can have upturned margins, and P. rufescens is the classic example of this character. Also, notice that the rhizines are separate, kind of ropy things. Both P. canina and P. rufescens have confluent, brushy, mat-forming things. Therefore I’m going to guess P. praetextata.
Other things to note in Peltigera species:
1) does upper surface have granules or powder in little round spots?
2) does upper surface have tiny scales? (especially along cracks and margins in old or damaged parts of thallus)
3) is upper surface smooth (under the wool) or is it roughened? (should be visible even at 10x)
4) are the apothecia flat disks, or are they curled up length-wise like saddles or fingers?
5) are the apothecia pure black or pale to dark reddish-brown?
6) are the veins distinct and raised, or are the broad and low or indistinct? (compare P. membranacea to P. polydactylon and P. malacea to see what this means)
I’ve posted a fair illustrated key to the North American species (many of which are cosmopolitan and occur in your area):
(Oops, I think my photo of P. ponojensis is wrong — I didn’t know the species well enough at the time…)
Created: 2010-11-26 11:19:15 CST (-0500)
Last modified: 2010-11-26 11:19:20 CST (-0500)
Viewed: 73 times, last viewed: 2017-03-21 06:00:09 CDT (-0400)