3-351 



:>3-05 



T 



40 



30 20 10 



% Laminarin (dry matter) 



Fig. 224 Gradients along the blade of (above) mannitol, (below) 

 laminarin in Laminaria saccharina. Note complete absence of 

 laminarin in basal young growing portion immediately above 

 meristem and reduction of mannitol in the older distal part of the 



blade. (After Black.) 



or enclosed bodies of water (Fig. 223). In Laminaria cloustoni the 

 seasonal variations are almost entirely confined to the frond. With 

 L. saccharina^ gradients in mannitol and laminarin occur along the 

 frond, the amounts appearing to be related to the age of the tissue 

 (Fig. 224). Mannitol and laminarin also vary with depth. In the 

 case of the Uttoral fucoids seasonal variations tended to increase 

 with increasing frequency of immersion. There is also a tendency 

 to more than one maximum in the mannitol and laminarin, due to 

 the interaction largely of exposure, temperature and formation of 

 reproductive organs. The low laminarin content in July /August of 



424 



