]52 BIOCHEMICAL SYSTEMATICS 



Agars These consist of two components: agarose, a 



linear polymer of galactose and anhydro- 

 galactose, and agaropectin, a sulfated poly- 

 saccharide. Agars set to thermally reversible 

 gels. 



Carrageenans These are also hexose-sulfate derivatives; 

 lambda carrageenan is a galactose sulfate and 

 kappa carrageenan is a mixture of anhydro- 

 galactose and galactose sulfate. 



Gelans Strong gel formers similar in structure to 



kappa carrageenan, but with a hexose-sulfate 

 ratio of about 0.5. 



Stoloff and Silva found that all species of the same genus pro- 

 duced the same type of soluble polysaccharide. In general, as indicated 

 in their paper, there are few cases of more than one type of poly- 

 saccharide occurring in the same family. Exceptions are as follows: 



Gelidiaceae Sulina produces gelan; four other genera, 



agar. 

 Endocladiaceae Glocopeltis produces carrageenan; Endo- 



cladia, agar. 

 Phyllophoraceae Gymnogongrus produces carrageenan; 



Phyllophora and Ahnfeltia, agar. 



Stoloff (1962) has reviewed the distribution of these poly- 

 saccharides and constructed a revised classification of the Florideae 

 on the basis of polysaccharide type alone. According to Stoloff the 

 taxonomist should "look up from his mounts and his microscope and 

 make fuller use of the technological advances in related disciplines. It 

 is not the tools but the viewpoints and objectives that should dis- 

 tinguish the botanist from the chemist or physicist." Later, Stoloff 

 says, "... at the familial level, and certainly at the generic level 

 of breakdown, the limits of usefulness of the evolutionary viewpoint 

 and the value to evolutionary theory seems to have been reached." 

 The present writers take a different view with respect to the lower 

 taxonomic categories, for it is in these that experimental methods, 

 cytogenetic, genetic and other macromolecular data are more appli- 

 cable. In any event it is not likely that the evolutionary viewpoint 

 will ever outlive its usefulness. 



A type of polysaccharide which is somewhat difficult to 

 classify, namely, amyloid, has been studied intensively from the sys- 

 tematic point of view by Kooiman (1960a) who has examined the 

 seeds of many species of higher plants. Amyloids are complex poly- 



