Seedlings of Thysanotus were inoculated in pot culture with fungi that form vesicular-arbuscular or ectomycorrhizas on other hosts. Mycorrhizas formed by both fungi were similar in morphology to each other and to mycorrhizas observed in field-collected plants. Hyphae of mycorrhizal fungi penetrated between epidermal cells and ramified between the cortex and epidermis. Spread of mycorrhizas in pot-cultured T. tenellus Endl. occurred only in the presence of a companion plant. In soils with low levels of nutrients, mycorrhizal plants of T. tenellus grew faster than non-mycorrhizal plants, with roots of infected plants growing relatively faster than shoots.