Phase contrast and polarised light micrograph of various tiny green algae, mostly Scenedesmus sp. green alga. Scenedesmus forms colonies of usually four or eight, unflagellated, elliptical cells arranged in rows, with a nucleus and a chloroplast with pyrenoid. The cells at the ends of the colonies often have spines as protection against feeding. Magnification: x186 when printed at 10 centimetres wide.