Orchid mycorrhizal fungi have been assumed to supply carbohydrates to the orchid seedlings with which they are associated. To do this they must be able to utilize a regular source of carbohydrate in the soil, and also to translocate soluble compounds to the orchids. Mycorrhizal Rhizoctonia spp. were shown to decompose filter paper cellulose in pure culture. Secondly, R. repens and R. solani, isolated from Dactylorchis purpurella, were able to compete with other soil micro-organisms in the exploitation of cellulose buried in unsterilized soil.