Describe the shape of the Spirogyra cells. Which cellular structure gives rise to this shape?

Spirogyra, otherwise known as pond silk, is a type of algae that can be found in bodies of freshwater. The cells are long, unbranched, and cylindrical, being much longer than they are wide. There is no distinction between the basal and distal end, and they connect to each multiple times over to create the "silk" they are seen as; they also can reproduce sexually and asexually. Each cell has one nucleus and a cell wall composed of pectin surrounded by cellulose. Inside each cell is a very distinct spiraling shape of green, being chloroplast strands. It is these shapes for which the cells are named.