Spirogyra Link in C.G. Nees: Water silk, pond silk. Zygnemataceae. Green algae. Bright green filamentous algae; free-floating and able to form cottony brown mats of pond scum at the surface. Found in shallow, quiet to slow-moving waters; common in ditches and along shorelines. Individual threads are made up of cylindrical cells and rarely branch; they feel slimy due to a mucilaginous coating. These filaments grow parallel to each other, rather than crossed or twisted. When held in the hands the algal mass is slippery and untangled, able to be separated into long strings or strands. Colonies floating in colder, deeper water look cloudy or dispersed around the edges; in shallow, warmer waters the algae tend to form firmer growths and produce dense mats. Under magnification a green spiral is seen winding around the interior of each cell; this is a chloroplast in the shape of a helix. Mats hinder swimming and fishing; these algae can be very problematic in irrigation and drainage canals.