Maize root slime is secreted by the outer root-cap cells. It is a complex of at least three polysaccharides, two of which are acidic and contain a high proportion of fucose. The polysaccharides are assembled and secreted by the endoplasmic reticulum and dictyosomes of the cells. It has been found that the synthesis of fucose-containing oligosaccharides takes place by an assembly of at least nine sugar residues on a polyprenyl diphosphate acceptor and this occurs at the endoplasmic reticulum. In addition, a glycoprotein carrying a large molecular mass carbohydrate portion containing fucose is synthesized mainly within the Golgi apparatus, although synthesis may be initiated in the endoplasmic reticulum. This glycoprotein could be an intermediate in the synthesis of slime polysaccharide, and the carbohydrate moiety of the glycoprotein may be assembled by transglycosylations from the polyprenyl diphosphate oligosaccharides.