I located the specimen in my collection and it became immediately obvious, on getting it under the scope, that it was nothing like Dicranella. In fact it is a very skinny Philonotis with shoots just a little over 1cm tall. I struggle to comprehend how I came to the conclusion that it was D. rufescens - I guess the red stem, small size and habitat were enough to convince me.
I'm not entirely sure which Philonotis it is. The shoots are somewhat falcate-secund which, coupled with their skinniness, suggests it could be P. caespitosa. I've checked the older leaves microscopically and none seem to be pleated, or with recurved margins, which fits with caespitosa rather than weedy fontana - but I'm not sure the cells are big enough. The photos below might help - if not I'd probably best pass the specimen on to Sam.
Just to add to the above - what looks like a double-tooth in the last photo is I think just an oddity, probably just two teeth very close together rather than a genuine double. I can't find any other teeth like it on those leaves I've checked under the microscope.
ReplyDeleteYou're certainly on the right tracks, looking at mature leaves among the tomentum. I suspect this is indeed P caespitosa, as P arnellii usually has longer, narrower leaves. What do the mamillae tell you?
ReplyDeleteThanks Sam. To be honest I struggled to find many mamillae - the cell contents had shrunk in this long-dry specimen and I found it hard to make them out. I'll have to have another look...
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