Observations on the fine structure of Coelastrum microporum

The fine structure of Coelastrum microporum is described with regard to its cytological organization. The cell wall of this organism is double-layered. Coating this wall is a multitude of short projections, termed "papillae," which together with certain gelatinous substances appear to bind the cells of the coenobium together The nucleus of a nondividing, vegetative cell shows a peripheral disposition and contains a single centrally located nucleolus Ribosomes are commonly associated with the outer membrane of the nuclear envelope. Individual cells contain a cup-shaped chloroplast with a single pyrenoid. The chloroplast is composed of interconnecting thylakoid stacks containing from three to 12 disks. The pyrenoid is always surrounded by starch, but several direct connections exist between the pyrenoid and the matrix of the chloroplast Elements of the endoplasmic reticulum are scarce. When observed, they are commonly coated with ribosomes About five parallel stacks of cisternae and associated vesicles constitute the dictyosomes. They are located immediately adjacent to the nucleus Mitochondria vary in size and possess tubular cristae Other structures present throughout the cytoplasm include vacuoles and lipid bodies.