A phylum of algae comprising the diatoms. These marine or freshwater unicellular organisms have cell walls (frustules) composed of pectin impregnated with silica and consisting of two halves, one overlapping the other. Diatoms are found in huge numbers in plankton and are important in the food chains of seas and rivers. Past deposition has resulted in diatomaceous earths (kieselguhr) and the oil reserves of these species have contributed to oil deposits. Diatoms are now included in the stramenopiles.
Subjects: Plant Sciences and Forestry.