244 MARINE FISHERIES OF NORTH CAROLINA 



naturally-occurring plants sometime during the summer. The material dis- 

 tributed would be expected to support plants the following year. 



NORTH CAROLINA AGARS 



Agars from Gracilaria confervoides and G. foliifera of North Carolina 

 both meet U. S. Pharmacopoeia requirements. They are similar to but not 

 identical with agar from Gelidium cartilagineum of California. Gel strength 

 of Gracilaria agar is more variable than that of Gelidium agar. Gracilaria 

 agar is somewhat more elastic and exhibits greater syneresis; its tempera- 

 ture of gelation, also variable, is between 45 and 63° C. as compared to 40 

 to 45° for Gelidium agar. The temperature of melting is about the same for 

 both types of agar. Because of the higher temperature of gelation and 

 greater syneresis, Gracilaria agar is less suitable than Gelidium agar for 

 culture media. Table 5 presents comparative data on Gracilaria agars from 

 various parts of the world and "Bacto" ^ agar from California Gelidium. 



TABLE 5 



Comparison of Properties of Gracilaria confervoides Agar from North Carolina and 

 Other Parts of the World and California Gelidium Agar. (From Stoloff, 1943) 



Concen. Temp, of Gel Strength 



percent gelation grams 



Grac. confervoides o 



from North Carolina i 



Grac. confervoides i 



from California i 



Grac. confervoides i 



from Austraha i 



Grac. confervoides i 



from South Africa i 



Difco "Bacto" agar i 



from Calif. Gelidium i 



113 



o . . 407 



5 43-59° C 650 



o 47 120 



5 • • 190 



o 46 95 



S ■• 167 



o 37 187 



5 337 



39 215 



5 350 



The gel strength given for North Carolina Gracilaria agar in Table 5 

 represents an extreme. Most samples are nearer the figures given for 

 "Bacto" agar; some are lower. 



Gracilaria agar from North Carolina seaweeds appears to be composed 

 of a mixture of "fractions," one or some of which gel at about 63° C. and 

 others at about 42°. Gracilaria agar usually forms an incipient gel at the 

 higher temperature but complete gelation does not occur until the tempera- 



I. A trade name. 



