At first I felt this was edging towards S. stellata, as I understand that this is the more common in the UK on herbaceous plants stems etc. However, I finally worked out that Bamboo is a grass and with it comes another possibility. The few records I can find and in Europe is that S. arundinacea is found on grasses and with Bamboo as one of the substrates. The spores are approx 145-150 x 2, the one measured here at 137µm is short of the final pinpoint end as you will see here. So longer. The apothecial margin to me isn't star shaped and mopre enclosed and rounded. The base of the asci did not chnage colour in Iodine, which cancels out S. radiata. Paraphyses are very slender with slight swelling at ends. Wondered if anyone esle had come across this species on grasses or Bamboo.

With thanks  Tony Hardware