Page:Popular Science Monthly Volume 12.djvu/687

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inches long, in the specimen from which this was sketched. Alluding to the difficulty in defining the species, Woolls says, "Botanists, from Robert Brown to Baron Müller, have endeavored to reduce the varying forms to systematic arrangement," but without success. And a vast amount of acumen and ingenuity has been brought to the task; such as the consideration of the operculum or cap of the flower-bud, and the length of the pistil. Compare the long pistil in the seed-vessel of E. Preissiana, left side of Fig. 1, with the short one in the

PSM V12 D687 Eucalyptus macrocarpa.jpg
Fig. 2.—Eucalyptus Macrocarpa.

flower of E. Globulus, in Fig. 3. The form of the anthers and the seed-vessels, and the texture of the bark, have all been taken as factors of the problem.

Owing to the bluish-green of its leaves, E. globulus is popularly known as the blue-gum tree. Abroad it is most known outside of its systematic name as the Tasmanian gum-tree, and Australian fever-tree. Among the settlers, gum-tree is the general name of the eucalypts. But, as might be expected of a genus so numerous in species, there are many trivial names, such as blue-gum, brown-gum, the red and the white mahogany, stringy-bark, and iron-bark, etc. The botanists reckon 150 varieties. These all belong to the great order Myrtaceæ, or myrtle-blooms. And a decidedly respectable relationship have these trees which shed "their medicinal gum," for they are close cousins to the well-known myrtle, the pomegranate, pimento, or allspice, cajeput, and clove. The flowers of this order are known in their structure as calycifloral. Perhaps this curious blending, or confusion, of the calyx and the corolla, is shown most interestingly in the flowers of these eucalypts. The calyx is really in two distinct parts, a woody cup below with an operculum or lid above. (See middle figure, bottom of cut 3.) When the flower is ready to open it pushes