Light micrograph (Spectral-Rheinberg contrast) of a single desmid, Micrasterias sp. , showing the elaborate, convoluted shape of the cellulose layer surrounding the two chloroplasts, and the division of the desmid into left & right halves. The term desmids is applied to a group of genera of green algae that show great morphological variety but are related by common features of cell structure and method of reproduction. Most desmids are unicellular, with a single nucleus and one or more chloroplasts (the site of photosynthesis within the cell). The cell walls all have a inner layer rich in cellulose & an outer, thickened pectin layer. Magnification: X 400 at 35mm size.