94 



THE METABOLISM OF ALGAE 



boiling^*® occurs in the Cryptophyceae and in Chilomonas 

 paramoecium appears to consist of about equal parts of 

 amylose and amylopectin.^^^ A polysaccharide, the presence 

 of which causes the chromatoplasm to stain reddish brown 

 with iodine, generally occurs in the Myxophyceae^^' 

 although it is not always demonstrable in these algae. 221 

 This polysaccharide, which has been generally considered 

 to be glycogen but which is perhaps better designated as 

 Myxophycean starch, evidently occurs in the cells in the 

 form of submicroscopic granules.^ '^ Oscillatoria princeps has 

 been found to contain an enzyme synthesizing a glycogen- 

 like polysaccharide having 14 to 16 glucose residues, which 

 may or may not be identical with Myxophycean starch, 

 from glucose- 1 -phosphate. ^•^^ Starch and similar sub- 

 stances appear to be absent from the Phaeophyceae. 



Another type of glucose polymer is represented by 

 laminarin, a soluble reserve product giving no colour with 

 iodine and occurring in the Phaeophyceae, e.g. in Asco- 

 phyllum, Fucus and Laminaria spp. to the extent of up to 

 25 per cent on a dry weight basis. ^^ Laminarin has been 

 reported as being absent from certain members of the 

 Phaeophyceae, e.g. Pelvetia canaliculata and Chorda and 

 Ectocarpiis spp.^'^ but this has been shown to be incorrect 

 in the case of the Pelvetia.^'' Normal laminarin is built up of 

 /5-D-glucopyranose units linked through C^ and C3 Upon 

 hydrolysis with mineral acid it yields a disaccharide, lamin- 

 aribiose or 3-/5-D-glucosyl D-glucose.^® Laminarin prob- 

 ably has the following constitution: ^^ 



CHPH 



HOH 



Laminarin may occur in another modification, the relation 

 of which to the normal form is not known.^^^^ 



