450 THE ALGAE 



aria saccharina used to be eaten and also young plants of dulse 

 {Rhodymenia palmata) in Scotland and Ireland. The weed of widest 

 use, however, was laver or Porphyra. This is interesting because in 

 Japan it is Porphyra that today forms one of the biggest crops for 

 cuHnary purposes. Here it is actually cultivated on bamboo poles 

 stuck into the shallow waters of bays and river mouths. The species 

 most commonly cultivated is Porphyra tenera and up to 50 sq. kilo- 

 metres may be occupied by these bamboo bundles, each Tarm' 

 being about 120 ft. x 7 ft. When the twigs have become covered 

 with a mass of sporeHngs they are pulled up and planted in an area 

 of low saUnity. When mature the algae are removed, dried and 

 pressed into sheets when it is known as Asakusa-nori. The other 

 important item of Japanese algal food is called kombu and is made 

 from the large laminarians, especially Laminar ia^, Alaria and Arth- 

 rothamnus. The kelp is gathered from open boats using special 

 hooks. When gathered it is dried and cut up in various ways so that 

 one can get shredded kombu, black or white pulpy kombu, filmy 

 kombu, hair kombu or sweet-cake kombu. The amount harvested 

 is considerable and in 1936 amounted to 293,284 tons of wet weed. 

 Other foods from brown seaweeds are Wakame from Undaria pin- 

 natifida, Arame from Eisenia bicyclis, Hijiki from Hijikia fust- 

 forme, Miru from the green Codium and a whole variety of lesser 



weeds. 



A similar extensive Hst of edible algae could be prepared for 

 Hawaii where the edible seaweeds are known as different types of 

 limu. At least 40 species are in common use, most of them being 

 small green or red algae. 



Some attempt has been made to assess the nutritional value of 

 these algae. Only an edible Nostoc from China, and the Japanese 

 Amanori (Porphyra) have a high nitrogen content, so that any value 

 must be in the carbohydrates and possibly the iodine. In general it 

 would appear that the algal foods are of more value to sick than to 

 healthy persons and the main use is in providing roughage in a diet 

 that is largely rice and fish. There is no doubt, however, that goitre 

 is not prevalent in these countries and this may well be due to the 

 amount of seaweed consumed. In recent years it has also become 

 known that many of the algae are quite rich in vitamins (cf. p. 414) 

 and they may be of importance in this connexion. 



The only other algal industry of any importance that should be 

 mentioned is the glue that comes from the Japanese red alga Gloio- 



