|The genus Eucalyptus was named in allusion to the operculum or lid which covers the calyx until the stamens are fully formed.
The plants are evergreen and vary from shrubs to trees of enormous height, some of them probably being the highest trees known. Kerner gives the height as 140 to 152 meters.
The leaves frequently vary in shape and in position on both young and mature trees; they are fixed vertically, and not horizontally as the leaves of our trees, the petiole being twisted. The leaves furthermore contain large oil-secreting reservoirs. The flowers are arranged in cymes or axillary umbels and are devoid of petals; the usually whitish stamens are inflexed in the bud and expand when the operculum is removed, giving the name as already stated to the genus. The fruit is a 3- to 6-celled truncated capsule, or pyxis. The seeds are small and very numerous, the sterile ones predominating.
Eucalyptus globulus is one of the largest known trees, attaining sometimes a height of 300 or even 350 feet, with a smooth, ash-colored bark. The leaves attain a foot in length, and vary, according to age, from a glaucous white to a bluish-green color. The flowers are large, pinkish-white, axillary, occurring singly, or in clusters. Although its wood is very resinous, hard, and durable, the tree is remarkable for the rapidity of its growth, reaching, under favorable circumstances, fifty feet of height in five or six years.
The leaves are described as follows:
Laminas lanceolately scythe-shaped, from 8 to 30 cm. in length and from 2 to 7.5 cm. in breadth; summits when present acute or acuminate; bases unequal, obtuse or more or less rounded and connected with a twisted petiole from 5 to 35 mm. in length; margins slightly uneven, revolute; coriaceous; both surfaces varying from pale yellowish-green to grayish-green and more or less glaucous, glabrous, glandular-punctate and with numerous small, circular, brown dots of cork; veins of the first order anastomosing with each other and forming a line nearly parallel with the margin.
Source: United States Dispensatory (1918)