To show the presence of nodules of nitrogen-fixing bacteria on the roots of legumes
Carefully spade up some leguminous plant like as clover, alfalfa, soy-beans, cow peas, etc. Take out the soil from the roots by washing with water. Observe the little white bumps or nodules on the roots. Nitrogen-fixing bacteria are inside these nodules. These bacteria take out nitrogen from the air and fix it in a form that enables plants to get it from the soil.