Tree tissue. It protects the trunk against the elements, disease, animal attack and fire. It is perforated by a large number of fine breathing pores called lenticels, through which oxygen diffuses. Bark is continually replaced by a living layer of cells called the cork cambium or phellogen. The London plane ("Platanus × acerifolia") periodically sheds its bark in large flakes. Similarly, the bark of the silver birch ("Betula pendula") peels off in strips. As the tree's girth expands, newer layers of bark are larger in circumference, and the older layers develop fissures in many species. In some trees such as the
Common buzzard Common buzzard The common buzzard ("Buteo buteo") is a medium-to-large bird of prey whose range covers most of Europe and extends into Asia. Over much of its range, it is resident year-round, but birds from the colder parts of the Northern Hemisphere typically migrate south (some well into the Southern Hemisphere) for the northern winter. The first formal description of the common buzzard was by the Swedish naturalist Carl Linnaeus in 1758 in the tenth edition of his "Systema Naturae" under the binomial name "Falco buteo". The genus "Buteo" was introduced by the French naturalist Bernard Germain de Lacépède in