American Lung
Association
You can visit this site for information on lung diseases in humans. Click on Diseases A to Z. What is sarcoidosis?
Leaves
Visit this site for art and descriptions of the parts of the leaf, and its functions as a plant organ. What are the three main functions of leaves?
Stems
At this site you can learn all about the structure and functions of tissues in plant stems. How many layers of cells form the epidermis of plant stems?