The important characters of diatoms are :
(a) They are basically unicellular but can form pseudofilaments and colonies.
(b) Diatoms may show gliding type of movements with the help of mucilage.
(c) The body is covered by a transparent siliceous shell known as frustule. The frustule is made of two valves, epitheca and hypotheca. The frustule possesses very fine markings, pits, pores and ridges.
(d) Each cell has a large central vacuole. The single large nucleus is commonly suspended in the central vacuole by means of cytoplasmic strands.
(e) Chloroplasts or chromotophores are yellowish brown to greenish brown. They contain chlorophyll a, chlorophyll c, p - carotene, fucoxanthin, distoxanthin, diadinoxanthin, etc.
(f) The food is reserved in the form of oils and leucosin. Volutin globules are also present.
(g) The common mode of multiplication is by binary fission.