I am an amateur trying to learn something about everything living in my garden
I promise to return to more sizable and familiar lifeforms soon, dear readers! For today's posting however: another lichen.
The lichen seen in photo 1 (click to enlarge) decorates many of the branches of my garden apple tree (at (1.2,1.5) - see here) and I'm almost certain (see shortly) in identifying it as Physcia tenella ('it' being either of the two greyish patches below the coin, as opposed to the yellow lichen left of the coin which - though I've not examined it is detail - is probably our old friend X. parietina)
The meaning of the Greek physcia (pronounced 'Fisk-ee-a') seems to be a matter of debate on the internet. I have come across it variously translated as "bellows", "breath-like", "sausage-shaped" and "blister"! Can anyone clarify the true meaning?
P.tenella is my blog's third example of a foliose lichen. According to my copy of the scholarly Lichens (F.S. Dobson, The Richmond Publishing Co.), Physcia lichens can be distinguished from other foliose lichens, in part, by their narrow (<~2mm) lobes, and septate spores (septa being thin, internal dividing walls - see here for some examples) - though I confess I've not looked for the latter.
Two further distinguishing features of P.tenella are i) the presence of eyelash-like cilia on the edges of the lobes. You can see these in the 40x-magnified photo 2. (Can anyone tell me what purpose it serves to lichen to 'sprout' these?) And ii) the presence of granular soredia (see here for my explanation of what these are) decorating the ends of the lobes. Were I to observe the soredia 'packaged' together inside little 'hoods' I understand I'd be looking at the closely similar lichen P.adscendens (since its not obvious they are, I'm sticking with my identification as P. tenella).
Finally, two nice facts about P.tenella I got from reading my copy of Lichens (O.Gilbert, The New Naturalist series). Firstly, P.tenella is one of three British lichen species favoured by long-tailed tits (Aegithalos caudatus) in building their nests (on average each nest contains nearly 3000 lichen flakes!). Secondly, being fairly acid- and nitrogen-tolerant (not all lichens are), in areas where people walk dogs, P.tenella is one of the commonest lichens to colonise the region marginal to that patch of tree-trunk known to professionals as "the canine zone" . It shouldn't be hard to imagine what this is!