Hi Shirl,
Sadly, pressure of work has kept me out of the forum for a while, but I have been interested to see this post. It relates directly to my own attempt to understand this group.
For what it's worth, I think this is much most likely to be one of the possibilities you already mentioned -
Cladonia pocillum.
Particularly in your 3rd photograph, bottom left, we get a view of the granules that does show that they are not only rather uniformly disk-like and flattened, but also there is the hint of a "skin" to them (said to be "corticate") rather than the texture of soredia which are derived from tissue below the surface of the cup. So on that basis (plus the lack of smaller soredia) I reject
C. chlorophaea and put this firmly in the
pocillum-pyxidata-monomorpha group.
It is not
monomorpha, which in any case is very rare in the UK and I am guessing your garden is not an acid dune-system, so that takes us to the very difficult
pyxidata-pocillum split. Here there is a real problem for Britsih lichenology as
C. pyxidata is supposed to be common, and it isn't! There is a fairly recent paper by Dutch lichenolgists in which they clarify the two species to some extent, and state they don't have true
C. pyxidata in the Netherlands at all, and also show that a number of published supposed to be it are actually
C. pocillum. Reading this paper has made me feel a lot better about the fact that I never seem to see satisfactory
C. pyxidata!
Anyhow, while I am not going to be 100% dogmatic on the basis of your photographs, the size and nature of the "basal squamules" (the scale-like structures that are on the ground around the cups) seem to me to be a much better fit to
C. pocillum. I also think all three photographs are the same species, though Poschiavanus has very wisely counselled caution and reminded us how often
Cladonia species grow together.
My thanks to Poschiavanus for the links to my site. I now have a page on
C. pocillum (
here) which shows a variant with more erect basal squamules, due to the nature of the site, but which is otherwise quite representative I think. On rock,
C. pocillum forms more flattened rosettes. Dobson's illustration is too recent for mention in the Dutch paper, but it seems to match true
C. pyxidata OK.
And Poschiavanus, we must know each other! Or else you have somehow found exactly the same group of lichens in Glen Quoich that were seen on this year's Kindrogan course.
Cladonia gracilis,
C. bellidiflora and
C. diversa all together between the rocks. Pages for the individual species are not on my site yet, but I have used exactly the same
C. bellidiflora individual in the banner on my main page. (A lot of
Cladonia to come, if/when I get time!) I also intended to go down for the Sorby NHS meeting but, sadly, preparing the paperwork for the latest new intake of students took up my time instead.
Alan