Summary:
Sirotrema parvula produces tiny fruiting bodies on Lophodermium pinastri on pine needles. It is not likely to be encountered casually, but was described from BC and is of intrinsic interest: the Sirotrema species appear to be intermediate between Sirobasidium (not in western North America) and Tremella.

Microscopic:
ballistospores "6-8 x 4-6 microns, oval or elliptic in side view, the large apiculus almost at the middle of the long axis, the side opposite the apiculus somewhat flattened", germination "by budding, by repetition, or infrequently by conjugation tube", blasto-basidiospores 6-9 x 2.5-3 microns, nearly cylindric to narrowly clavate [club-shaped], rounded distally, tapered slightly basally, the narrow attachment point typically truncate, "budded off repeatedly, arising directly from basidial compartments or at ends of epibasidia", germination by budding; probasidia (6.5)8-13(15) x 6-8(11) microns, predominantly spherical to nearly spherical, some ellipsoid, "becoming 4-celled, initially single and terminally on fertile hyphae, proliferation laterally then producing a dense cluster of basidia, some basidia also developing from contiguous cells or through direct expansion of basal clamps of other basidia", epibasidia "often lacking if blasto-basidiospores are produced, but usually present and 10-80 x 1.5-2 microns", hymenium up to 66 microns thick; subhymenial hyphae "with frequent septa, 1.5-3 microns wide, the cells immediately below basidia often swollen to 6-8 microns"; context hyphae in mature fruiting bodies 1.5-3 microns wide between clamp connections, the clamp area mostly swollen to 4-6 microns, "branched, the branches arising directly from hyphal filaments or from clamps", clamp connections usually with large openings, clamp complexes of 2-4 closely fused clamps often present, haustorial branches mainly in basal parts of the fruiting body, often with 2 filaments (1 terminal, 1 basal)

Notes:
includes BC

Synonyms and Alternate Names:
Exidia rolleyi Olive