Eucalypts: Oil Glands
When held up to the light, oil glands in eucalypt leaves are visible with the naked eye.
Oil glands are characteristic of the family Myrtaceae and can be observed in other genera such as
Callistemon (bottle brush) and Leptospermum (tea tree). As a consequence of their oils,
sclerophyllous
plants are highly flammable;
however, these plants are well-adapted to the frequent fires that are fuelled to a considerable extent by these oils.
The oils are volatile, and fill the air with a characteristic smell on warm days.
Oil glands have several functions: they contain poisons that deter herbivores; they make leaves inflammable;
and they may be used as a storage area for waste products.
Eucalyptus oil formed in leaf oil glands consists mostly of cineole, and is known to repel many herbivores.
click on line across image above to see another transverse section of a leaf, this time showing oil glands.