No, despite appearances to the contrary, I have not gone away! My camera has been kept busy over summer snapping pictures of a host of interesting creatures in my garden and it's high time I resumed the task of writing about them.
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A quick look in my mushroom guide and I'm fairly confident my mushroom is a Collared Parachute Marasmius rotula.
I say 'fairly confident' as Marasmius bulliardii is similar in appearance though I read it is typically somewhat smaller than rotula and grows on leaves . You can find pictures of both, plus various other species, on the splendid Bioimages site and a key to some 60+ Marasmius species on Michael Kuo's site.
Had I gone to the trouble of taking a spore print (see my previous posting here), and assuming my mushroom is indeed M.rotula, I'd have found the spore colour was white. Under the microscope the spores are 7-10um x 3-4um in size and elliptical.
Turning to my copy of the excellent Fungi (Spooner and Roberts, publ. Collins) a nice thing to learn about Marasmius mushrooms is that one of them is amongst the world's oldest toadstools. A Marasimus-like mushroom ('Archeomarasiumus liggetti') was found, trapped in a 90 million year old piece of amber, in New Jersey by one David Hibbett, a Harvard mycologist. The American Museum of Natural History webpage carries a photo and Hibbett's webpage includes a link to his 1997 paper on the discovery ('Fossil mushrooms from the Cretaceous and Miocene ambers and the evolution of homobasidiomycetes' ).
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