Direct observation of fungal aggregates in sand dune soil.

The mycorrhizal fungus Glomerus in association with bean hosts, Phaseolus vulgaris L., growing in pot cultures and grass hosts, Calamovilfa longiflora (Hook). Scribn and Andropogon sp. growing on Lake Huron sand dunes produced extensive external mycelium. This mycelium was the dominant factor in the aggregation of soil particles. Light and scanning electron microscope studies indicated that the sand grains were attached to the hyphae. An amorphous deposit was often present at the interfaces of sand grains and hyphae. It appeared to act as an adhesive. Staining procedures indicated that this material contained polysaccharide. Other microogranisms were observed in association with the Glomus hyphae and the amorphous deposits.