The composition of the capsular polysaccharides (CPS) and exopolysaccharides (EPS) of three strains of Arthrobacter globiformis, isolated from the leaf cavities of Azolla caroliniana (strain B1), A. filiculoides (strains A3 and L1) and A. globiformis ATCC 8010 have been analysed by HPLC and enzymatic assays. Glucose and galactose were detected in the EPS of all the strains, while rhamnose was present only in the EPS of the strain L1 and uronic acids in B1 and ATCC 8010. Traces of fructose were detected by enzymatic assays in all the strains. The CPS contained glucose, galactose and rhamnose, while uronic acids were present only in strain B1. In all the strains the amount of EPS was higher than CPS. The reactivity to different dyes and lectins of the mucilagineous matrix of the algal packets extracted from the fern and of the bacterial mucilage were similar.