From the study on Extraction, purification and characterization of haemagglutinin (lectin) of some Indian seaweeds , 21 seaweeds (Bryopsis plumose, Caulerpa microphysa, C. racemosa, C. scalpelliformis, C. lateverens, Enteromorpha compressa, Ulva lactuca, Dictyota bartayresiana, Padina tetrastromatica, Sargassum longifolium, S. wightii, Acanthophora spicifera, Centroceras clavulatum, Champia globulifera, Cheilosporum spectabile, Gracilaria corticata, G.crassa, G. edulis, Hypnea valentiae and Laurentia poiteaui) were collected from the Gulf of Mannar Biosphere Reserve during September 1999 and assayed for haemagglutinin activity using different blood samples. Influence of enzyme (papain) treatment of blood cells on agglutination activity was also assessed. The amino acids of ASL and GCL detected presently were compared with the amino acids of other algal lectins reported earlier, presence of cystine in marine algal lectins has been found out for the first time in India.