Eucalyptus L’Hér.

>800 species worldwide, all but 16 endemic to Aust., all states and territories

Trees, tall shrubs or mallees. Bark either smooth throughout, or partly rough and partly smooth or rough throughout. Smooth-barked plants are referred to as gums but they may have some rough bark near the base or patches of rough (fibrous, flaky or ribbony) bark hanging loosely on the upper trunk or branches. Rough bark either with long matted fibres which can be removed in strings or ropes several centimetres or even metres long (stringbarks or mahoganies); or shortly fibrous, flaky or scaly (peppermints, boxes, scalybarks); or the fibres short and dark coloured or black and often impregnated with kino (ironbarks). Juvenile leaves (on seedlings and sometimes on mature branches and trunks which have been damaged) opposite, sometimes sessile or stem-clasping, differing from the adult leaves. Adult leaves usually alternate, petiolate, mostly with visible oil glands, usually isobilateral but sometimes paler underneath; venation usually prominent; midrib distinct and intramarginal veins usually present; lateral veins parallel or irregular and leaving the midrib at angles of 10–60° or forming a fine reticulation. Inflorescence usually a cymose umbel of 3, 7, 11, 15, 19, etc., up to 35 flowers or fewer by abortion, usually pedunculate in the leaf axils, or the umbels in axillary or terminal panicles. Flowers sessile or pedicellate. Calyx and corolla fused into a single structure, the operculum, or the calyx absent and a single petaline operculum present or calyx and corolla segments separately connate into two opercula. Operculua seated on the rim of the floral tube and usually leaving a scar when shed. Stamens numerous, in 2 or several rows. Anthers versatile or adnate; pollen sacs parallel or divergent and confluent at the apex, dehiscing by longitudinal slits or terminal pores; connective usually with a gland on the back or near the apex. Ovary 2–7-locular. Fruit a capsule enclosed by the floral tube except at the summit, opening by terminal valves which are either exserted or enclosed by the free portion of the floral tube. (Fig. 36). Floral tube usually smooth at maturity, rarely with longitudinal ribs, bearing at the summit the operculum scar or double scars, the scar of the filament bases, and within these a disc which is convex flat depressed or enclosed within the floral tube. (Fig. 36). (Some species have sucker leaves that have neither adult nor juvenile characteristics. Be careful that you are observing the leaves of the correct type. You will often find capsules, and even buds, on the ground underneath the canopy of the tree that you are attempting to identify. Make sure that they have not fallen from an adjacent tree. Leaf dimensions are length x width.)