Keel (bird anatomy) keel; and ratites (from "ratis", "raft" — referring to the flatness of the sternum), having a subtle keel structure or lacking one entirely. However, this classification has fallen into disuse as evolutionary studies have shown that many flightless birds have evolved from flighted birds. The current definition of Carinatae now includes all extant birds. Keel (bird anatomy) A keel or carina (plural carinae) in bird anatomy is an extension of the sternum (breastbone) which runs axially along the midline of the sternum and extends outward, perpendicular to the plane of the ribs. The keel provides an anchor to which a
Plant anatomy Pflanzen", describing microscopic studies of plant tissues. In 1813 a Swiss botanist, Augustin Pyrame de Candolle, published "Théorie élémentaire de la botanique", in which he argued that plant anatomy, not physiology, ought to be the sole basis for plant classification. Using a scientific basis, he established structural criteria for defining and separating plant genera. In 1830, Franz Meyen published "Phytotomie", the first comprehensive review of plant anatomy. In 1838 German botanist Matthias Jakob Schleiden, published "Contributions to Phytogenesis", stating, "the lower plants all consist of one cell, while the higher plants are composed of (many) individual cells" thus confirming and