Spirogyra algal strand. Confocal light micrograph of a filament of Spirogyra sp. green algae. This alga forms slimy threads called water-silk" or "mermaid's tresses" in stagnant or slow moving water. The filament is made up of elongated cells (two whole ones seen) that secrete a mucilaginous substance which binds adjacent filaments. Each cell contains one or more chloroplasts, arranged in spiral bands (green). The chloroplasts contain green chlorophyll pigments and are the sites of photosynthesis in each cell. Magnification x170 when printed 10cm high."