(F.V.M., in Report Acclm. Soc., Vict., 20, 1870.) Giant Gum-tree.

Systematic. - A tree at last stupendously tall; bark outside whitish and smooth except at the stem base; leaves of young seedlings opposite, sessile, cordate-roundish, whitish from waxy bloom; leaves of rather thin texture, from elongate to broad lanceolate, much unilaterally curved, shining on both sides their secondary venules slightly spreading; oil-dots extremely numerous and pellucid; umbels mostly solitary.

Fruit. - "Quite small, generally semi-ovate its border depressed or nearly flat; valves enclosed."

The fruits are rather smaller than E. Delegatensis, which they somewhat resemble in shape.

Habitat. Victoria; Tasmania.

REMARKS. - The description given here is taken verbatim from Mueller's "Dichotomous Key to Victorian Plants," and is so explicit that that botanist must have had a strong species in view at the time of founding E. regnans. Deane and Maiden (Proc. Linn. Soc, N.S.W., 1899, p. 460) synonymise their own species, E.fastigata, with it; but as it is impossible to reconcile the Baron's description with the specific characters of their tree, a Eucalypt well known to us we retain the two as distinct species. The tree known as E. regnans in Tasmania has quite a smooth bark, while E. fastigata has a stringy bark. Maiden (Crit. Rev., vol. I, p. 184) still later adheres to his classification of E. fastigata.

ESSENTIAL OIL. - Material for distillation was collected on Mt Wellington, Tasmania, in July, 1908. One sample of leaves with terminal branchlets was collected at a height of about 2,000 feet above sea-level, and another at about 2,500 feet. This tree is known locally in Tasmania as "Swamp Gum." The oils from both consignments were alike, showing that a difference in alt tude has little influence on the secreted oil. The composition of the oil was also in agreement with that of E. regnans, from material sent for distillation from Yarra Junction, Victoria, by Cuming, Smith, and Company. This agreement is shown by the appended results, and is particularly marked with those derived from the several fractions. The comparative absence of dextro-rotatory pinene in the oil of E. regnans shows it to be a species distinct from E. fastigata, irrespective of botanical differences.

The oil of E. regnans consists largely of the terpene phellandrene, and contains a fair quantity of the stearoptene eudesmol. This substance was obtained in larger amount than is usual, by increasing the pressure of steam after the oil had distilled off in the usual manner; on allowing the distillate to remain for some hours in open vessels, the eudesmol could be removed as a crystalline fat-like mass from the surface of the water, and purified in the ordinary way.

The presence of cineol was doubtful even in the portion distilling at about 1760 C, so that this frequently occurring constituent in Eucalyptus oils was only present in traces in that of E. regnans. The ester appeared to be almost entirely geranyl-acetate, as it saponified readily in the cold with two hours' contact. The ketone piperitone was only present in small amount. A considerable portion of the oil consisted of high-boiling constituents, probably the sesquiterpene largely; and the high-boiling fraction soon became solid after separation, due to the presence of the eudesmol.

The crude oils were reddish in colour, due to the action of the phenols on the iron derived from the still; on removing the colour, the oil was of a light . primrose tint. The two samples of oil had the following characters: -

One of these oils was then rectified, and the results are here tabulated with those obtained with the oil of this species from Yarra Junction in Victoria. Both oils commenced to distil at 1700 C. (corr.).

The higher laevo-rotation of the first fraction, above that of the second fraction, together with other indications that dextro-rotatory pinene was not present, and the absence of cineol show the oil of this species not to agree with that of E. fastigata. The saponification number of the Victorian oil was 12.4. The comparatively small yield of oil from the leaves and branchlets of E. regnans renders the species of little value as an oil-producing tree.

As there was a strong indication for alcoholic bodies in this oil, the Tasmanian samples were mixed and a portion acetylated in the usual way. The saponification number was then 73.2, while in the cold with two hours' contact it was 31.5. This result indicates that about 16 per cent. of free eudesmol and 5 per cent. free geraniol were present at that time.

The results of this investigation with the Tasmanian material were published by us in the Proc. Roy. Soc, Tasmania, October, 1912.