(F.v.M., in Edit. Bailey in Synopsis Queensland Flora, 176, 1883.) Lemon-scented Ironbark.

Systematic. - A medium-sized tree with glaucous foliage. Leaves ovate to lanceolate, usually under 5 inches long, obtuse, sometimes shortly pointed; venation fairly distinct, especially on the under surface, intramarginal vein looped, usually well removed from the edge, but sometimes quite close, lateral veins spreading, inclined at about 450 to the mid-rib. Peduncles axillary or lateral, 4 to 6 lines long, each with three to six flowers, often in terminal panicles. Buds glaucous; calyx tube semi-ovate, contracted to a slender pedicel; operculum conical.

Fruit. - Semi-ovoid to hemispherical, on slender pedicels; rim thin; valves slightly exserted; about 2 1/2 lines long and 2 lines in diameter.

Perhaps the two fruits closest in morphological affinity are E. intertexta (some forms) and E. melliodora.

Habitat.-Palmer River, Queensland.

ESSENTIAL OIL. - The oil of this species of Eucalyptus is abnormal, as it contains the aldehyde citral in some quantity. The oil was referred to by Schimmel & Co., in the year 1888 (Semi-Annual Report), the specific gravity being recorded as 9.880 and the boiling point from 170-2300 C.

In the first edition of this work this Eucalypt does not appear, because it was not possible at that time to procure material for distillation, as the species grows in country not easy of access. Efforts since made to procure material for investigation have been successful, and through the kindness of the late Mr. Ingham, the Queensland distiller, and Mr. J. L. Adams, Chemist, of Cooktown, leaves were collected on the Palmer River, Queensland. They had to be brought many miles by carrier to the nearest railway station, then forwarded to Cooktown, and afterwards by sea to Sydney.

The principal terpene occurring in the oil of this species was lævo-rotatory limonene, and both pinene and phellandrene appeared to be absent. Cineol could not be detected. The oil had some resemblance in its physical properties to lemon oil, the optical activity, however, being in the reverse direction. The amount of citral was not great, although more abundant than in lemon oil, but does not correspond in this respect to the oil of Backhousia citriodora or even to that obtained from Leptospermum Liversidgei (Proc. Roy. Soc. N.S.W., December, 1905). The amount of free alcohol (most probably geraniol) was somewhat large, and the secondary odour of the oil, when freed from the aldehydes, resembled that of geraniol very markedly. The ester was most probably wholly geranyl-acetate, particularly as this substance occurs plentifully in Eucalyptus oils. The high refractive index of the higher-boiling portion indicated that the sesquiterpene was also present, although the results do not allow room for much of that constituent. The crude oil was of a light lemon colour, was mobile, and very aromatic, the citral and free geraniol combining to give it a pleasant and refreshing odour, without the slightest resemblance to that of ordinary Eucalyptus oil as known in pharmacy.

The material, which consisted of leaves and terminal branchlets, had been more carefully collected than would be the case commercially, and as the leaves were quite dry, the yield may be considered a maximum one. Thirty-one ounces of oil were obtained from 78 lb. of material, equal to 2.48 per cent. It may reasonably be supposed that the oil of this species will eventually become of some commercial importance when better known. Comparative tests for flavouring purposes with the rectified product compared very favourably with the best lemon oil, both for culinary purposes and in the manufacture of lemonades.

The crude oil had specific gravity at 150 C. = 0.8715; rotation aD - 37.53°; refractive index at 20° = 1.4814, and was soluble in 8 volumes 80 per cent, alcohol. Saponification number for esters and free acid was 8.6.

On rectification, only a few drops came over below 175° C. (corr.). Between 175-1930, 65 per cent, distilled; between 193-265°, 23 per cent, distilled; at higher temperature the distillate was quite acid. These fractions gave the following results: -

The portion boiling below 193 was again fractionated. Nothing came over below 1750 C. (corr.) but 40 per cent. of the fraction distilled between 175-1770, and 23 per cent. between 177-1790; between 179-184° 17 per cent. distilled. These fractions gave the following results: -

Plate LXXX.

W. Marshall, del.

Eucalyptus Staigeriana, F.v.M. Lemon Scented Ironbark

The tetrabromide was formed in the usual way with the fraction distilling at 175-177°, and when purified melted at 104-105° C. It thus appears that the terpene present in the oil of this Eucalyptus was almost entirely lævo-rotatory limonene, and that over 60 per cent. of the oil consisted of that substance.

An aldehyde determination on the crude oil, using a 30 per cent. solution of sodium bisulphite, gave an absorption equal to 16 per cent. of citral. This aldehyde when purified formed the characteristic naphthocinchoninic acid by Doebner's reaction, the product melting at 198° C.

The non-aldehydic oil, which was quite aromatic, had a secondary odour of geraniol. It had specific gravity at 15° C. = 0.8710; rotation aD -- 46.8°; refractive index at 20° = 1.4802.

The saponification number for the esters and free acid in the non-aldehydic oil was 28.3, or 9.9 per cent. of ester, if calculated as geranyl-acetate, equal to 8.3 per cent. in the original oil.

A portion of the non-aldehydic oil was acetylated in the usual way, when the saponification number had risen to 78.5, representing 13.8 per cent, free alcohol, calculated as geraniol, or 11.6 per cent. on the original oil.

The results of this investigation were originally published in the Pharmaceutical Journal, London, March, 1906.