Polarised light micrograph of Pandorina sp. green algae and Fragilaria and Synedra sp. diatoms. Pandorina consists of up to thirty two cells joined at their bases to form a colony. Diatoms are a type of algae and form a significant portion of the Earth's biomass, generating about 20 to 50 per cent of the oxygen produced on the planet each year. Magnification: x372 when printed at 10 centimetres wide.