False-colour scanning electron micrograph (SEM) of nitrogen-fixing bacteria, Rhizobium leguminosarum (orange cylinders), on the root hair of a pea plant, Pisum sativum. Rhizobium is a free-living soil bacterium for most of its life, but at times forms a symbiotic association with the roots of leguminous plants. In return for breaking down atmospheric nitrogen & converting it into a form the plant can use, the bacterium gains access to the plant's carbohydrate food stores & is kept safe in the plant's tissue. Magnification: x5'600 at 35mm, x11'200 at 6x7cm size. (More detailed information available on request). Reference: MICROCOSMOS, page 98.