Ichthyostomum pygmaeum
(Bulbophyllum pygmaeum)

- a very small orchid, usually found growing on tree trunks, along with mosses. Leaves are about 5mm long and 3mm wide.

The round yellow-green things are pseudobulbs, and these are linked by rhizomes to form a mat.

The flower is tiny - about 1.5-2mm across, and often does not open, being self-pollinating. It took me weeks of looking at many plants before I found this one with an open flower.