found in agar preparations fromGracilariaverrucosa . Its content varied with the culture conditions and with the tissue age. Highly substituted portions having this residue were obtained by enzymic degradation with β-agarase I. Permethylation analysis and 13 C-n.m.r. spectroscopy demonstrated the linkage of this sugar to O-6 of the 3- O -linked- d -galactopyranose units. The definition of agar should