Light micrograph of filaments of Spirogyra, a green alga which forms slimy threads called water- silk" or "mermaid's tresses" in stagnant or slow moving water, becoming abundant in spring or autumn. The filaments are made up of elongated cells which secrete a mucilaginous substance which binds adjacent cells. Each cell contains one or more chloroplasts, arranged in spiral bands. The chloroplasts house the green chlorophyll pigments & are sites of photosynthesis within each cell. Magnification unknown."