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
Jesuit's bark Jesuit's bark Jesuit's Bark, also known as cinchona bark, as Peruvian Bark, and as China Bark, is a former name of the most celebrated specific remedy for all forms of malaria. It is so named because it was obtained from the bark of several species of the genus "Cinchona", of the Rubiaceae family, that have been discovered at different times and are indigenous in the Western Andes of South America and were first described and introduced by Jesuit priests who did missionary work in Peru. Other terms referring to this preparation and its source were "Jesuit's Tree", "Jesuit's Powder" and