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
Terminalia sericea to tall. The bark is a reddish or greyish brown colour and peels away in strips. The bluish-green leaves tend to be clustered at the tips of the branches. They are ovate with entire margins and both the upper and lower surfaces are clothed in silvery hairs. The flowers are white and are borne in short axilliary spikes. They have an unpleasant smell and may be pollinated by flies. The fruit are winged nuts containing a single seed and turn a darker pink colour as they ripen. They may remain attached to the branch for a year and are dispersed