(Hook, f., in Flora Tasmania, 1859.) Red Gum, White Swamp Gum.

Systematic. - A tree about 30 feet in height, with a rough untidy dark-coloured bark; the bark on the branches is smooth and clean. Abnormal leaves ovate or oval, thin, petiolate; venation reticulate, intramarginal vein looped at some distance from the edge. Normal leaves oval to ovate or lanceolate, older leaves thick and shining; venation not prominent, especially in older leaves, intramarginal vein well removed from the edge. Flowers in umbels of about four to eight, peduncles about 4 lines long, sometimes axillary or springing alternately and independently from the stem, giving the inflorescence the appearance of a panicle. Buds about 3 lines long; calyx tube conical, tapering to a very short pedicel, and about twice as long as the blunt conical operculum.

Fruit. - Conical, turbinate; rim convex, outer edge sometimes protruding and giving the fruit a bell-shaped appearance; valves occasionally exserted; about 3 lines long and 2 lines broad.

The nearest in shape to these are E. paludosa and E. camphora, but not E. ovata. Those illustrated are rather larger than generally obtains.

Habitat. - Tasmania (Red Gum) and South Australia (White Swamp Gum).

REMARKS. - Morphologically the herbarium material has a resemblance to E. paludosa, R.T.B., a mainland species described in 1898 (Proc. Linn. Soc, N.S.W.), and especially are the fruits alike. Maiden (Proc. Linn. Soc, N.S.W., 1901), in a paper on E. Gunnii, Hook, f., places both the mainland E. paludosa, R.T.B., and the Tasmanian E. acervula, Hook, f., under E. Gunnii. The results of this investigation show that these three are distinct both botanically and chemically. E. paludosa, R.T.B., has a smooth bark, whilst E. acervula, Sieb., has mostly a rough bark, and could perhaps on occasions be classified with the Hemiphloæ group of Eucalvpts. "The tree has usually a very bushy top, and the leaves arc of rather a pendulous growth (L. G. Irby), while E. paludosa is a fine typical tree, with stout outstretching branches and a straight stem. The abnormal leaves are very different in appearance, shape, and colour from those of E. Gunnii, from which species it also differs in the number of flowers in the umbel, bark, timber, and chemical constituents. From our investigations it would appear that the chief differences between E. acervula. Hook, f., and E. paludosa, R.T.B., are the timber and bark and chemical constituents. E. acervula timber is harder, closer grained, and altogether superior to that of E. paludosa.

ESSENTIAL OIL. - Material for distillation was collected at Hobart, Tasmania, in April, 1912. The yield of oil was 0.2 per cent. The crude oil was reddish in colour, had an odour reminding one of geranyl-acetate, and resembled in some respects the oil of E. Macarthuri, of New South Wales. The chief constituents were dextro-rotatory pinene, lævo-rotatory phellandrene, cineol, geranyl-acetate, free geraniol, together with a small amount of an undetermined alcohol, and its ester, and also a solid paraffin-like stearoptene. A substance of such a character had not previously been recorded for Eucalyptus oils; it is not, however, peculiar to this species, for it has already been found in the oils of some New South Wales Eucalypts. It most probably belongs to the CnH.2n+2 group, as it is saturated. This solid aliphatic stearoptene is related to a similar substance found in Rose oil, although melting at a higher temperature, and it is remarkable that the principal alcohol in both Rose oil and in the oil of this Eucalypt is geraniol. The oil of E. Macarthuri, however, does not contain it. Similar paraffins, with varying melting points, have been isolated from the oils of a few other plants, and in some cases from the oils of their leaves. The stearoptene from E. acervula is without doubt from the oil of the leaves, because the trees were not in flower at this time of the year.

The oil of E. acervula does not agree entirely in general characters with that of E. paludosa of New South Wales, as the former contains a small quantity of phellandrene and not much pinene, while the principal terpene in the oil of E. paludosa is pinene, and phellandrene appears to be absent. The esters, too, were not identical in composition. They both contained, however, about the same amount of cineol, and the paraffin stearoptene was also found in both, but in much smaller quantity in the oil of E. paludosa. The two species may, therefore, be considered as closely related.

The specific gravity of the crude oil at 150 C. = 0.8956; rotation aD - 1.1°; refractive index at 200 = 1.4747, and it was soluble in 1 volume 80 per cent. alcohol, but became turbid with 4 volumes, and remained turbid with further addition of alcohol in the cold, forming a flocculent precipitate on standing. On heating the solution it became clear, but the paraffin was deposited again on cooling.

The saponification number for the esters and free acid was 32.8 by boiling, and 21.4 in the cold with two hours' contact; this represents 7.5 per cent. of geranyl-acetate in the crude oil, and 4 per cent. of another ester if calculated for an alcohol having a similar molecular weight. The odour of geraniol in the separated oil, after saponification, was very pronounced, and although the amount of oil at our disposal did not permit of its separation and purification, yet there is no doubt as to its identity, particularly as geraniol and geranyl-acetate are such common constituents in certain classes of Eucalyptus oils.

The amount of free geraniol in the oil was considerable, and another undetermined alcohol was also present. A portion of the crude oil was acetylated by boiling with acetic anhydride and anhydrous sodium-acetate in the usual manner; the separated oil was mobile, and had an odour of geranyl-acetate. The saponification number for this esterised oil by boiling was 105.3, and in the cold with two hours' contact, 69.5. This latter figure represents 24.3 per cent, of ester as geranyl-acetate, and indicates that 13.2 per cent. of free geraniol was present in the oil, as well as 6.6 per cent. of another alcohol, assumed to have the same molecular weight.

It is worthy of notice that over 50 years ago, when this species was described by Hooker in his "Flora Tasmaniæ," he remarked that "The bruised foliage has a much sweeter odour than is usual in the Genus." The discovery of geraniol and its ester in the oil not only confirms this remark, but also indicates the constant character of the chemical constituents.

The acid in the original ester was separated and found to be almost entirely acetic.

On rectification, a little acid water and rather a larger amount of objectionable smelling volatile aldehydes came over below 175 ° C. (corr.). Between 175-2000, 42 per cent. distilled; between 200-228°, 8 per cent, came over; the thermometer then quickly rose to 255°, and between that temperature and 185°, 36 per cent, distilled. These fractions gave the following results: -

The residue, when poured from the still, became solid when cold; it was boiled in alcohol and the alcohol separated while hot; on cooling, a crystalline paraffin-like substance separated.

To prove the presence of pinene, another 100 c.c. of the oil were distilled, the added two fractions gave 32 c.c. distilling below 170° C. (corr.); it was again distilled, when 15 c.c. was obtained below 162°. This contained some cineol, which was removed by shaking with 50 per cent, resorcinol. The remaining 9 c.c. of oil had a pinene odour; specific gravity at 15° C. = 0.8594; rotation aD 4+10°; and refractive index at 20° = 1.4690. A small quantity of phel-landrene was still present, but this did not interfere with the formation of the nitrosochloride; which when purified, melted at the correct temperature for the pinene compound.

The cineol was determined by the resorcinol method in the portion of oil distilling below 195° C.; the result indicated that 21 per cent, was present in the crude oil. The high-boiling constituent was most probably the sesquiterpene.

Material of this species was also obtained at Little Swanport, Tasmania, in June, 1908. The oil was practically identical with that of the above sample, with the exception that a little more pinene was present at this time of the year. The specific gravity at 15° C. = 0.898, and the refractive index at 20° = 1.4724. The saponification number for ester and free acid was 34.3, and the ester consisted mostly of geranyl-acetate. The oil contained the paraffin-like substance in slightly larger amount than did the Hobart sample.

The investigation of the oil of this species was published by us in the Proceedings of the Royal Society of Tasmania, in October, 1912.

In September, 1916, we received material of this species for distillation from South Australia, through the kindness of Mr. Walter Gill, the Conservator of Forests of that State.

The oil was practically identical with that previously distilled from this species growing in Tasmania. This was particularly noticeable through the esters and the solid paraffin, although it contained more of the sesquiterpene.

The crude oil had specific gravity at 15° C. = 0.930; rotation aD - 1.4°; refractive index at 20° = 1.4870, and was soluble in 1 volume 80 per cent, alcohol, but with excess precipitated the paraffin.

Geranyl-acetate was present to the extent of 14 per cent., as the saponification number, in the cold with two hours' contact, was 40.7.