Book excerpt: An illustrated guide to the houseplants you need for clean and fresh air when you're stuck at home How clean is the air you breathe? Plants are the lungs of the earth: they produce the oxygen that makes life possible, add precious moisture and filter toxins. Houseplants can perform these essential functions in your home or office with the same efficiency as a rainforest in our biosphere. In this beautifully illustrated guide, noted scientist Dr Bill Wolverton shows you how to grow 50 plants that filter the most common pollutants, making it easy for you to purify the environments that impact you the most.