| Summary: | 1.1. The polysaccharides of two Antarctic brown algae have been studied. 2.1. Ascoseira has been chemically investigated for the first time. 2.2. After extraction of traces of mannitol and some monosaccharides, sequential extraction with aqueous Ca Clg, dilute acid and dilute alkali gave mixtures of laminaran, "fucan" and alginate in unusually low total recovery. 2.3. Laminaran fractions from the aqueous and alkali extracts contained different proportions of 3-(l->3)- and 3-(l->6)- linked units, with evidence of branching in both fractions. 2.4. The "fucans" contained varying proportions of fucose, galactose and glucuronic acid, small amounts of xylose, mannose and glucose, and half-ester sulphate and protein. 2.5. The alginate in the aqueous extract contained about 75% mannuronate residues, that of the alkali extract about 80% guluronate residues. Direct alkaline extraction gave a low molecular weight alginate with a mannuronate to guluronate ratio of about 0.45 and only a small proportion of sequences of alternating residues. 3.1 The mucilaginous exudate, and the "fucan" therein, from the kelp Macrocystis pyrifera have been found to be physically and chemically similar to the same materials from a Californian sample of M. pyrifera. 3.2. Sequential extraction of the Antarctic sample gave "fucan", alginate and a trace of laminaran. 3.3. The "fucan" in the aqueous CaC extract was shownby partial hydrolysis to be composed of subunits containing about 70% fucose, varying small proportions of xylose, mannose, glucose, galactose and glucuronic acid, and half-ester sulphate and protein. Sulphate was linked only to fucose, and predominantly to carbon atom 4. Further partial hydrolysis gave complex fragments with evidence of mutual and various linkages of most of the monosaccharide residues. Tentative evidence of covalent linkage of protein and polysaccharide was found. 3.4. Direct alkaline extraction of Antarctic M. pyrifera gave a high molecular weight alginate with a mannuronate to guluronate ratio of about ...
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