of the foregoing techniques. However, after germi- 

 nation the plant grows to maturity with a little mor- 

 tality. If some devices are used to plant young hiids 

 in large quantities, the efficiency will he quite reli- 

 able. Trials of this method are now underway. 



LA\fI\ARIA 



Biology 



Important species are Laminaria japonica and L. 



ani;iisuita. L.japonicd is the best quality though not 

 much is produced. HalfofallZ.£(/;;//;^//7« harvested is 

 L. a ng us tat a var. longissima. 



Laminaria mature in the fall. Some hundred mil- 

 lion zoospores, each having two cilia, come out from 

 a frond. A germling is a microscopic filiment. When 

 the water temperature goes to 10°C or below in 

 winter, the germling gives rise to spermatia and eggs. 

 A fertilized egg germinates and grows into a 

 Laminaria plant. The filaments do not fruit at water 

 temperature over 10°C and for this reason Laminaria 

 grows only in northern Japan. 



Young plants are seen in early spring, then grow 

 rapidly, but start to decay from the top of the frond in 

 the autumn. In the second year, a growth at the top 

 of the stipe develops and becomes a second year's 

 blade. The growth in the spring is good at 5°-I5°C, 

 but never takes place at over 20°C in the summer. 

 The second year's blades are the main parts of the 

 plant harvested because the firsi year's blades are of 

 unsuitable quality for consumption in Japan. 



Harvesting 



The harvesting season is from July to August. A 

 drying process after harvesting is important to get an 

 excellent product. Hokkaido is subjected to foggy 

 days frequently: therefore, the drying by a drier is 

 useful for increasing production and for improving 

 quality. 



Culture Techniques 



Shinran-shonin. an old famous Buddhist priest, is 

 said to have been the first to propagate Laminaria in 

 1718. At present a large amount of the national ex- 

 penditure is invested in Hokkaido. 



Throwing stones into the sea for propagation im- 

 provement has been practiced for many years with 

 good results. The yield rate in the area where stones 

 are thrown is roughly the same as the one in natural 

 growing districts. The area in which this technique is 



used should not be one in which the bottom is altered 

 by the movement of sands. Use of a short cylinder of 

 concrete which was thrown into the sea was prac- 

 ticed on a large-scale basis at Nemuro, Hokkaido. 

 The expense is supposed to be recovered in 7-8 yr. 

 The reefs which are too high to drain the even 

 surface are dynamited so that Laminaria plants are 

 able to grow. To eliminate harmful weeds such as 

 Phyllospadix from the bed bottom explosives are 

 also useful. An explosive equivalent to 150-31)0 g of 

 dynamite has an effective area of about 4 m-. 



Cultivation 



China is said to produce .30,000 tons oi Laminaria 

 annually due to the recent progress in cultivation to 

 produce a dietary balance. 



In Japan the emphasis has been on increasing the 

 production of Laminaria plants which grow nat- 

 urally in the sea, because it supplied sufficient 

 amounts for the demand of consumers. With in- 

 crease of consumption and rise of market price, 

 cultivation has been attempted. 



There are some obstacles preventing a break- 

 through in Laminaria cultivation, especially the fact 

 that the plant takes 2 yr to grow into a desirable 

 market product for Japanese consumers, i.e., 2 yr 

 plants. Research is now going on to reduce this 

 period. 



GELIDIUM (AND OTHER AGAR WEEDS) 



Introduction 



The production of raw seaweeds for agar-agar in 

 recent years has been 6,500 tons dry weight and 

 5,500 tons are imported. The latter, sold at a cheap 

 price though not of good quality, replaced the ones 

 raised in Japan. Agar output was 5,500 pounds in 

 1963. Korea which exported raw materials in prewar 

 days is now producing more agar-agar every year 

 and soon is going to exceed Japan's production. 



Biology 



Raw seaweeds for producing agar belong to the 

 families of Gelidiaceae and Gracilariaceae. Of 

 these. Geliclium amansii is the most important 

 species. It grows between low tide level and 20- to 

 30-m depth. They are found in areas which are influ- 

 enced by warm currents. More than 609?^ of the total 

 production comes from Izu Peninsula and Izu Is- 

 lands, where the rock of the andesite, clear water. 



14 



