STUDIES ON AGAK-AGAR IN JAPAN 217 



of Corallinaceae (10) and Helposiphonia (II). Some Gastropoda were 

 found to feed on them (11). Research is now being carried out in co- 

 operation with phycologists on the ecological relationship between Geli- 

 dium and Corallinaceae. 



Some trials to "cultivate" these algae have been made. Kinoshita 

 and Hirobe(12) v^jere successful in seeding the spores of Gracilaria 

 confervoides on an experimental scale. Fujimori hung the Gelidium 

 plants on hemp-palm rope from a bamboo buoy in a calm inlet. He 

 found that the plant grew twice as much in weight every month of the 

 late winter as it had in the preceding month (S. Suto). 



II. The Relation between Jelly-strength and Chemical 

 Constituents of Agar-substances 



Generally speaking, mucilages of red algae (geloses) are ester-sul- 

 phates of galactan, but there are in fact various kinds. After studying 

 each gelose for each kind of red algae, the following results have been 

 obtained: The more sulphuric acid is combined in it the weaker is 

 the jelly-strength obtained, and vice versa. Sulphuric acid content va- 

 ries widely from 1 to 25% (13). There are two kinds of sulphuric acid 

 combined, one of which remains in the ash when the geloses are burnt 

 while the other does not. Sulphuric acids are combined in geloses by 

 two types, one of which is R-SO^-R' and the other R-SO4-M (R being 

 polysaccharide and M metal). Analysing geloses of many kinds of red- 

 algae, and representing the results on a graph having a mel-ratio of 

 hexose/total SO3 as its ordinate and that of total SO3/SO3 in ash as its 

 abscissa, we get a line nearly parallel to the ordinate for geloses of all 

 red-algae which have sufficiently strong jelly-strength to be utilized as 

 material for agar-agar, and similarly we get a line parallel to the abs- 

 cissa for geloses of red algae having little jelly-strength and which are 

 utilized for stiffening textiles. At the same time, geloses of these kinds 

 of red algae v/hich have a weaker jelly-strength are found to be repre- 

 sented by a line located intermediately between the two above-men- 

 tioned lines (13). Moreover, when gelose (SO3 ca. 9%) of a kind of 

 Gracilaria confervoides, represented by the intermediate line, is treated 

 with dilute alkali solution, a part of the sulphuric acid is easily sepa- 

 rated, resulting in an increase of jelly-strength. Those which have 9% 

 sulphuric acid are very weak in jelly-strength, but when the sulphuric 

 acid content is finally reduced to 2% (comparable with that of agar- 

 agar), jelly-strength increases remarkably so as to be comparable with 

 that of agar-agar (14). It is also reported (15) that the addition of 



