ALGAL UTILIZATION 451 



peltis furcata and known as funori. The species occurs wild but can 

 also be cultivated by building up the shore to the right level at 

 which the alga grows. The glue is obtained by dissolving the alga 

 in hot water, the extractable material having been given the name 

 of Funorin. 



It is clear that there are a whole group of algal substances which 

 are termed phycocolloids, and which fall into three categories : 



{a) water soluble ethereal sulphates such as agar; 



(h) water soluble reserves such as laminarin; 



(c) alkah-soluble polyuronides such as alginic acid. 

 A tentative arrangement of these substances is shown in the ac- 

 companying schema (p. 452). 



The need to produce alginates and also agar during the 1939-45 

 War led to a survey of the world's supplies. Previously only the 

 Pacific coast of North America had been surveyed in connexion 

 with the development of the kelp industry there thirty years earlier. 

 Extensive surveys of the Macrocystis beds were made in New Zea- 

 land and also of the rock-weed {Fucus, Ascophyllum) and oar weeds 

 {Laminaria spp.) in Great Britain. This work has gone on steadily 

 since the war and additional surveys have been made in other con- 

 tinental countries. Grapnel, echo-sounder and aerial photography 

 have all been employed in these surveys, the last-named being 

 perhaps the most successful, especially when combined with grap- 

 nel sampUng. The more recent work has demonstrated how in 

 Scotland, at least, the weed density falls off with depth and that 

 there is also a mathematical relationship between depth and weed 

 density for any given area. The cover around Scotland is about 87 

 per cent at one fathom, 60 per cent from 4-6 fathoms, 25 per cent 

 from 7-8 fathoms and is commonly zero by the time 9 fathoms are 

 reached. 



Since the war, much work has been carried out on the biology of 

 those seaweeds that are of commercial importance. This appHes 

 particularly to species ofFucus and Laminaria^ and also to Porphyra, 

 Gelidium and Gloiopeltis in Japan, and agarophyte algae in all parts 

 of the world. Most of tliis work has been directed to a study of 

 regeneration from perennial, basal holdfasts and to conditions of 

 reproduction. There is still a great deal more that needs to be 

 carried out and much of the earlier work on chemical composition 

 requires to be repeated. 



In recent years the alga Chlorella has assumed great importance 



