Isolates of Sebacina vermifera Oberwinkler (Tremellaceae), identified by their teleomorphs, from orchid and non-orchid hosts have been examined for their mycorrhizal associations. All isolates stimulated germination of seed of species of Microtis (Orchidaceae). Three isolates from ectomycorrhizal hosts formed ectomycorrhizas on Melaleuca uneinata R. Br. ex Alton I. and other ectomycorrhizal plants. None of the orchid isolates nor an isolate which was endophytic in Phyllanthus formed ectomycorrhizas but in addition to species of Micron's they stimulated germination of one or more species of Caladenia, Cyrtostylis or Glossodia but not other terrestrial orchids.
Protocorms of Microtis developed at depth in soil in the presence but not the absence of ectomycorrhizal S. vermifera on M. uneinata. Young albino plants of Microtis rara R. Br. grew for 4 months in the presence of ectomycorrhizal S. vermifera with M. uneinata but mycorrhizal albino plants on their own all died, suggesting a possible tripartite mycorrhizal association.