Tree pine ("Pinus" species) the bark exudes sticky resin which deters attackers whereas in rubber trees ("Hevea brasiliensis") it is a milky latex that oozes out. The quinine bark tree ("Cinchona officinalis") contains bitter substances to make the bark unpalatable. Large tree-like plants with lignified trunks in the Pteridophyta, Arecales, Cycadophyta and Poales such as the tree ferns, palms, cycads and bamboos have different structures and outer coverings. Although the bark functions as a protective barrier, it is itself attacked by boring insects such as beetles. These lay their eggs in crevices and the larvae chew their way through the cellulose
Tree fork forms in a tree and bark is incorporated into the join, this is referred to as an 'included bark junction' or 'bark inclusion'. A common cause of bark being incorporated into the junction is that the junction is braced by the touching of branches or stems set above that junction (in arboriculture, these branch interactions are termed 'natural braces'). Such included bark junctions can be substantially weaker in strength than normal tree forks, and can become a significant hazard in a tree, particularly when the bracing branches are shaded out or pruned out of the tree. Research has shown that