Seagrasses possess similar organs and tissues as the other flowering plants. Nearly all-mature flowering plants have distinctive above and below ground parts. The exceptions are some pleustophytes such as the Lemnaceae and representatives of the genus Ceratophyllum, and haptophytes such as the Podostemaceae. Below ground parts normally consist of roots for anchoring and rhizomes/stems for mechanical support. Above ground parts usually constitute shoots bearing several leaves. A leaf usually has a basal sheath for protecting the apical meristem and developing leaves, and a distal blade for producing food by photosynthesis and giving off water vapor through transpiration.