The organic component of the cell wall of the marine diatom Melosira nummuloides (Dillw.) C. Ag

Organic material which may be several layers thick has been found beneath the siliceous cell wall of the marine centric diatom Melosira nummuloides (Dillw.) C. Ag. This supports the findings of Liebisch (1928, 1929). The organic component, thought to be polysaccharide, is deposited outside the plasmalemma after the siliceous component has been laid down. It exists as two distinct entities, one associated with each valve.