Chrysophytes

The Chrysophytes include the diatoms and the golden algae (desmids). They are found in fresh water as well as in marine environments. They are microscopic and float passively in water currents — that is, they form part of the plankton. Most of them are photosynthetic.

In diatoms, the cell walls form two thin overlapping shells, which fit together as in a soap box. The walls are embedded with silica and are therefore indestructible. Because of this, diatoms have left behind large amounts of cell wall deposits in their habitat; this accumulation over billions of years is referred to as 'diatomaceous earth'. Being gritty, this soil is used in polishing and in the ** …