The bacillariophyceae, popularly called diatoms, form a very important group of both fresh water and marine unicellular algae. There are about 16000 species of algae present in this group.The shape and size of these algae vary greatly. This may be in the form of boots, circles, triangles, squares etc. Sometimes the unicellular forms unite by a gelatinous material to form small colonies.
- Fresh water and marine algae. Majority are unicellular and some are multicellular and colonial.
- Cells are eukaryotic.
- Chief pigments are chlorophyll a, beta carotene, and xanthophylls.
- Reserve food includes fats and volutins.
- Sexual reproduction is a special type, with the formation of auxospores.
- Male gametes are flagellate, with 1 or 2 flagella.
- Life cycle is diplontic.