CABBOHYDBATES OF THALLOPHYTA AND BBYOPHYTA 55 



ia also present. Here, too, after inversion there is an 

 increase in the dextrorotatory power of the solution ac- 

 companied by a rise in its reducing-power, both pointing 

 to the presence of laminarin. The traces of fucosan Kylin 

 mentions could not show an increase in the discrepancy 

 between the values obtained by reduction and by polariza- 

 tion before and after inversion. None of his quantitative 

 results lend themselves to the view that sucrose is ever- 

 present in these algae, for inversion invariably increases 

 the dextrorotation of the solution. It is possible, however, 

 that the presence of a little sucrose might be quite masked 

 in this respect by a preponderating quantity of laminarin. 

 His work on fucosan has shown that this substance is 

 not, as was believed, a carbohydrate reserve material 

 occurring in highly refractive globules. It is, however, a 

 tannin, but not a typical one, since it is not precipitated 

 by ferric chloride, though it does give a dark brown colour 

 with this reagent. In solution it has an astringent taste, 

 a strong reducing action, and is precipitated by neutral lead 

 acetate and by lime-water even when acids are present. 

 In alkaline solution it is quickly oxidized to a brown sub- 

 stance, which under the name of phycophsein was formerly 

 considered to be a water-soluble chromatophore pigment. 

 This, however, Molisch (1905) and Tswett (1906) had al- 

 ready shown to be a post-mortem oxidation product, though 

 its relation to fucosan was not suspected. When warmed 

 with dilute mineral acid fucosan yields no sugar, and ac- 

 cordingly cannot be a glucoside. 



As a reserve material the polysaccharide laminarin plays 

 the part in this group that starch does in the higher plants 

 and in the red algse. Kylin prepared this substance in a 

 pure condition, and found it to have the specific rotation 

 a D = - 13-15, presumably at the temperature of his labora- 

 tory; as before mentioned, laminarin gives only glucose on 



