What is the ‘gum’ in a gum tree?

(8 September 2017) A eucalyptus tree dripping sap is not a happy plant. The ‘gum’ produced by eucalyptus trees, called ‘kino’, is a protection against an invasion of borer insects… or against any other damage to the bark. Its red colour stands out, especially on the white outside of the scribbly eucalypts.
Another eucalyptus, the famous bloodwood, also derived its name from the higher concentration of kino in its bark. The ironbark species is hard, rough, and deeply furrowed. It is impregnated with dried kino (a sap exuded by the tree) which gives a dark red or even black colour.
Kino resembles red-currant jelly, but hardens in a few hours after exposure to the air and sun to form an amber-like material. It has no smell, but a very astringent taste. Eucalyptus kino is used by Australian aborigines in a tea for treating colds.
Australia is the country of origin of all eucalyptus trees in the world. In the 1850s, Eucalyptus trees were introduced to California by Australians during the California Gold Rush, and over the past 200 years eucalyptus have spread all over the world because of transport by humans

Technique
No special remarks. Handheld, flash light photo.