Ultrastructural Observation of the Surface Coat of Dunaliella Tertiolecta From Staining With Cationic Dyes and Enzyme Treatments*

SUMMARY The surface coat of the cell‐wall‐lacking alga Dunaliella tertiolecta has been examined with the use of the cationic dyes, alcian blue and ruthenium red. The previously undetected existence of a glycocalyx‐type cell envelope is described. The results from enzymic digestions suggest a gross similarity in the biochemical nature of the coat of Dunaliella with that reported for other eukaryotic cell types. The biological significance of this surface coat is discussed in relation to the absence of a rigid cell wall and the known ability of such algae to withstand extreme changes in the osmotic potential of the growth medium.