INTERCELLULAR SUBSTANCES AND WALLS 



85 



saccharide, fucoidin, is a 1,2-a-polymer containing residues of the 

 methylpentose, L-fucose, esterified with sulfuric acid. 



The rhodophycean wall contains cellulose together with gelatin- 

 ous polygalactose sulfate esters. Best known of these polysaccha- 

 rides is agar, which consists of D-galactose units joined via 1,3-link- 

 ages with L-galactose sulfate. The ratio of D-galactose: L-galactose 

 sulfate lies between 9:1 and 7.5:1. 



The fundamental cellulose-pectin pattern is found in the Cyano- 

 phyta. The presence of chitin has been claimed, but continues to 

 be in doubt. 



Our consideration of the algale cell wall has encompassed 

 several protozoan groups. A number of algal forms have also 

 received zoological recognition as flagellates (class Mastigophora) 

 of the sub-class Phytomastigina. 



The systematic relationships among these forms may be sum- 

 marized as follows: 



Botanical system 

 Phylum Class 



Zoological system 

 Order (all sub-class Phytomastigina) 



Cholorophyta 

 Pyrrophyta 



Chrysophyta 



Chlorophyceae 

 Cryptophceae 

 Dinophceae 

 Chrysophyceae 



Volvocina 

 Cryptomonadina 

 Dinoflagellata 

 Chrysomonadina 



Many Protozoa are ameboid, or possess an external "wall", 

 the pellicle, of uncertain properties and constitution. Mineralized 

 structures which serve as shells or as externally formed skeletons 

 have been developed among the ameboid forms of the Sarcodina 

 in the orders Foraminifera and Radiolaria. 



The foraminiferan shell may be composed of nitrogenous mater- 

 ials or siliceous plates, but is commonly calcareous in nature, and 

 often similar in form to the molluscan shell. As they grow, the 

 radiolarians commonly form intricate spicular structures at their 

 surfaces. These structures may exist as a lattice work at the surface, 

 or may consist of several concentric lattice-spheres, the innermost 



