Flat circular plates 214-6 inches in diameter with a wall of 3/8 inch, made in pairs, one being slightly greater in size and forming a lid for the smaller plate, into which melted culture medium is poured and allowed to set. Petri dishes may be of glass (sterilized by heat) or transparent plastic material (sterilized by gas or gamma ray treatment), and provide a convenient apparatus for the study and isolation of growing bacteria, especially of their colonial form.
Shallow, circular glass dishes, usually 10 cm in diameter, which are used in bacteriology laboratories for the growth of micro-organisms.