Scanning electron micrograph of two types of bread mould, Penicillium sp. & Mucor mucedo, growing on the surface of a slice of bread. Spores circulate freely in the air. When they alight on a favourable medium, they germinate an extensive network of hyphae (threads), the function of which is to absorb nourishment for growth & for the production of spores. The picture shows a sprinkling of single spores; some have germinated to form a mass of hyphae. Spores may be borne in saclike structures called sporangia, as in Mucor (globular bodies), or directly on the hyphae as in Penicillium (feathery) structures. Magnification X100 (at 10x8 size).