(Labill, Voy. I, 153, t. XIII.) Blue Gum.

Systematic. - A lofty tree with a smooth, whitish-blue bark. Abnormal leaves sessile, or shortly petiolate, cordate, covered (as also the twigs) with a glaucous bloom. Normal leaves lanceolate, falcate, 9 inches to 1 foot long, rather thick; venation prominent, lateral veins spreading, oblique, intramarginal vein removed from the edge. Flowers large, generally occurring in threes, in the axils of the leaves, sessile or on very short thick pedicels. Calyx tube broadly turbinate, thick woody, more or less ribbed and rugose or warty or nearly smooth, 1/2 to 3/4 inch diameter; operculum flattened, surmounted by a thick centre, warty. A smooth secondary operculum is often found in this species.

Fruit. - Hemispherical or cup shaped, tuberculate, and strongly ribbed; rim rounded or quite flat and broad, and a pronounced groove below the edge; valves short, depressed or exserted .... Up to 3/4 inch long and 1 inch in diameter or more.

A fruit easily distinguished from any other of the genus. A small, smooth fruited form that has a wide distribution, and seed distributed abroad, is not E. globulus but E. St. Johni, R.T.B.

Habitat. - Occurs in isolated patches on the southern half of the coast range of New South Wales; Tasmania; Victoria.

REMARKS. No species of Eucalypt has received so much attention, both from botanists and chemists, as this particular tree. Mueller devotes several pages to it in his Eucalyptographia, and as his figure of the species is excellent, it is reproduced here. The large white or cream-coloured flowers, the warted sessile fruits, the two opercula, the square branchlets, and the glaucous sessile abnormal leaves are all characteristic features. It is one of the Tasmanian species which also occur on the mainland of Australia, and has a fairly wide distribution in the south-eastern parts, extending as far north in this State as Mount Corricudgy. The tree is a very rapid grower, and for this reason is extensively planted in California and South Africa, where timber is in very great request for the mines and fuel. The wood is pale-coloured, fairly hard, easily worked, but difficult to season. Its occurrence in this State is patchy and so not much used for oil distillation. It has been extensively planted in Algeria and in Europe, and the oil from the former locality enters into competition with the Australian product.

ESSENTIAL OIL. - Leaves and terminal branchlets for distillation were obtained from Jenolan, N.S.W., in August, 1900. The yield of oil was 0.92 per cent. The crude oil was but little coloured, and had the characteristic odour of all those belonging to the richer cineol-pinene class of the "Gum" group of Eucalypts. The oil was rich in cineol, contained some pinene, but phellandrene was absent. Eudesmol was detected in very small amount in the higher boiling portions, and the sesquiterpene was also present in the oil boiling above 2600 C.

The crude oil had specific gravity at 150 C. - 0.913; rotation aD + 8.4°; refractive index at 200 = 1.4663, and was soluble in 1 1/2 volumes 70 per cent, alcohol. The saponification number for the esters and free acid was 2.1.

On rectification, 2 per cent. distilled below 1650 C. (corr.). This portion consisted largely of volatile aldehydes with some acid water. Between 165-183°, 87 per cent. distilled; between 183-260°, 4 per cent, came over. and between 260-270°, 2 per cent, distilled. These fractions gave the following results: -

The cineol, determined by the phosphoric acid method in the first fraction and calculated for crude oil, was 57 per cent. (O.M.) By the rapid phosphoric acid method, determined in February, 1920, the result was 64 per cent.

It will be seen from these results that the oil we distilled from E. globulus, growing naturally in New South Wales, was similar in character and constituents to those always obtained with the oil of this species, no matter where the trees are found growing naturally. This comparative constancy in the chemical product of identical species of Eucalyptus is one of the most interesting results brought to light by this research. This constancy in constituents is not peculiar to the oil of E. globulus alone, but is common to the several members of the genus, and innumerable instances of this fact are recorded in this work. It has been, we think, this constancy of constituents that enabled the oil of E. globulus originally to command such favourable consideration from those dealing in Eucalyptus oils. It is an illustration of the advisability of restricting operations to species the oils of which are in most request, and of keeping the product of individual species distinct. If this be done, then the quality of any Eucalyptus oil can be assured, and the industry become of greater importance, the species name being a guarantee of the constancy of the product; the purchaser could then be sure of obtaining what is required. That this method is a judicious one has been illustrated over and over again, more particularly, perhaps, with the oils of E. Macarthuri, E. polybracka, and E. Australiana. Nothing can be more detrimental than the indiscriminate mixing of oils of the various Eucalypts, and if more than one species belonging to the same chemical group are being worked, it would even then be better to keep the products distinct, although the oils may be in agreement. The advantages to be derived from such a procedure will be more fully recognised when cultivation of Eucalyptus species for their oil products shall become more general. Eucalyptus globulus belongs to a group of cineol-pinene oil yielding trees, of which many occur in Australia, the oils of which are often not easily distinguishable from each other. Commercially-distilled Eucalyptus oils ought, therefore, to be supplied with that constancy of constituents and physical characters which have so long been characteristic of the product of E. globulus. Very little oil of this species is now distilled in Australia, as the products of more prolific yielding species have supplanted it, the higher yields of oil of these species alone being answerable for this.

Plate XLVI.

Eucalyptus Globulus. Labill

Tasmanian Blue Gum

(After Mueller.)