(DC, Prod., iii, 217.) Grey Gum.

Systematic. - A large tree, with a dirty looking, smoothish, or friable bark, and rectangular branchlets. Abnormal leaves ovate, lanceolate, often shortly acuminate, 4 to 6 inches long, pale coloured on the underside, sometimes almost oblique, membraneous, margins recurved; venation distinct, oblique, spreading. Normal leaves lanceolate, sometimes oblique, pale on the underside, varying in length and breadth up to 6 inches and 2 inches respectively, thinly coriaceous; venation not pronounced, lateral veins fine, oblique, parallel, intra-marginal vein close to the edge. Peduncles axillary, flattened, under 6 lines long, about six flowers in the umbel. Calyx in the bud stage angular, conical; in the flower stage hemispherical; operculum conical or hemispherical, and much acuminate, under 3 lines long.

Fruit. - Turbinate to hemispherical, pedicel thick, short; rim thick, domed; valves obtuse, well exserted and pale; 4 lines in diameter.

They are quite specific; the dark slightly domed rim is the more common and easily distinguished, but occasionally the rim is truncate, giving the capsule an E. resinifera appearance.

Habitat. - Coast districts of New South Wales and Queensland.

93 Eucalyptus punctata 148

REMARKS. This is one of the best-known trees in the neighbourhood of Sydney, where its common appellation is "Grey Gum." The bark is characteristic, and although classed as smooth, yet is perhaps the dirtiest looking bark to be found amongst the smooth-barks or Gums, in the older trees it becomes dark, rugose, variegated, and exudes manna (H. G. Smith; see Paper in Proc. Roy. Soc, N.S.W., Vol. 31, p. 177), as well as the leaves. The mountain varieties are separated under the varietal names of didyma and major.

ESSENTIAL OIL. -During the months of May and June, 1897, a somewhat extensive investigation was undertaken on the oil of this species, and considerable material distilled, which had been collected from individual trees in various stages of growth. The results with the different samples of oil obtained during that investigation will be found tabulated in a later article. The results of this investigation were first submitted by us to the Royal Society of New South Wales, and are published in the proceedings XXXI, p. 259. All the oils contained similar constituents, and these only varied slightly in amounts, this variation accounting for the slight differences in physical properties. With general material even these slight alterations would be minimised and a closer uniformity in general characters observed. The oil of this species of Eucalyptus was rich in cineol, contained pinene, but phellandrene was absent. Aromadendral was present in small amount in the various samples, but was a little more pronounced in some than in others.

To arrive at the constitution and general character of the oil of this species, equal volumes of the crude oils of all the samples were mixed together, and the resulting product analysed. The mean yield of oil from all the material was 0.8 per cent. This crude mixed oil had specific gravity at 150 C. = 0.9160; rotation aD + 0.85°; refractive index at 200 = 1.4717, and was soluble in 1 1/4 volumes 70 per cent, alcohol. The saponification number for the esters and free acid was 18.8.

On rectification 1 per cent. distilled below 1670 C. (corr.). Between 167-1720, 30 per cent. distilled; between 172-1830, 58 per cent. distilled. These fractions gave the following results: -

First fraction, sp. gr. at 15o C.

=

0.0910;

rotation aD

+

2.15°

Second

"

"

"

=

0.09156;

"

+

1.1°.

The cineol, determined by the phosphoric acid method in the second fraction, was 62 per cent., and in the crude oil 55 per cent. (O.M.).

The rectified oil was slightly tinged yellow, a character usual with the oils of this group, and is apparently due to the influence of the predominant phenol present in these oils.

The material from which the several.oils were distilled was collected from (a) one fair-sized tree; (b) one large tree; (c) abnormal leaves; (d) from a large tree; (e) from old trees mixed; (f) from young trees 20-30 feet high, mixed; (g) from medium trees mixed; (h) from one medium-sized tree; (i) from one very fine tree, the leaves of which were divided into two equal parts and distilled separately. All the above material was collected near Sydney.

The whole of the oils distilled for the above investigation were mixed together, a portion kept in the dark, and in September, 1919, twenty-two years afterwards, this oil was again analysed. It had not altered much during that long period, except that the specific gravity was a little higher, but the cineol apparently had not increased in amount. On rectification 82 per cent, distilled below 1900 C. The crude oil and large fraction gave the following results: -

Crude oil, sp. gr. at 150 C.

=

0.9337; rotation aD + 0.8°; refractive index at 20° = 1.4724.

Large fraction

"

"

=

0.9147; rotation aD + 1.6°; refractive index at 200 = 1.4639.

The cineol was determined by the resorcinol method in the large fraction and calculated for the crude oil; the amount was 65 per cent. By the rapid phosphoric acid method it was 55 per cent., when calculated for the crude oil.

Plate LI

93 Eucalyptus punctata 149

Eucalyptus Punctata. D.C. Grey Gum