SummaryThe mucilaginous material, which forms a layer several microns thick around plant roots, contains a glucan, a polyuronide, and heterogeneous polysaccharides. An assessment is given of the effects of the mucilage on ion and water uptake by plants, on soil chemical and physical properties including aggregation, and as an energy source for microorganisms. It is concluded that these effects are important but that more chemical and physical studies of plant mucilage are required.