Light micrograph of two filaments of the freshwater green algae Spirogyra. The algae is divided into cylindrical cells, joined end to end to form an unbranched filament. Within the cell walls are the spirally wound chloroplasts (green) where photosynthesis occurs. In addition, each of the cells contains a nucleus suspended in the centre by cytoplasmic strands. A large vacuole is also present, containing a solution of sugars, mineral ions and amino acids. A small quantity of peripheral cytoplasm exists. Spirogyra reproduces asexually by cell division & sexual by conjugation. Magnification: x80 at 6x4.5cm size.