(F.v.M., Proc. Linn. Soc, N.S.W., 1889, p. 1020, t. XXVIII and XXIX.)

A Blue Gum

Systematic. - Known as "Blue Gum" and "Spotted Gum" in different localities, and erroneously recorded as E. globulus from the Araluen district. It is always a tall straight growing tree, attaining a height up to 150 or even 200 feet, with a diameter up to 4 feet, with a smooth bark, chalky white, or bluish, hence its name "Blue Gum." The abnormal leaves are very large, glaucous or even chalky white, round, or heart shaped, sessile and stem-clasping on the sharply angular and winged branchlets, gradually becoming alternate, petiolate, lanceolate to elongate, and often very narrow lanceolate, more or less curved. The normal leaves often attain a length of 12 inches or more, much resembling those of E. goniocalyx, F.v.M., but not quite so lustrous on the upper surface; venation distinct, intramarginal vein removed from the edge. Peduncle axillary, short, much flattened. Flowers few, sessile. Calyx angular or flattened; operculum much constricted, tuberculated.

Fruit. - Pedicellate or sessile, turbinate to slightly hemispherical; rim thick; valves slightly exserted; about 4 lines in diameter.

They resemble some forms of E. globulus and the species is probably a local variation of that Eucalypt.

Habitat. - Victoria to the Blue Mountains, New South Wales. On the ranges at an elevation from 1,000 feet to 2,000 feet, generally in the poor forest land, and often on steep mountain sides.

REMARKS. - E. Maideni resembles E. globulus and E. goniocalyx in general appearance, and is not readily distinguished from the latter, with which it grows associated on the mountain slopes, the trunks and foliage of the two having much the same appearance. They differ, however, in their fruits and young state leaves, so that there is little difficulty in distinguishing them. They also differ in their timber, for while that of E. goniocalyx is of a dirty brown colour, the timber of E. Maideni is of a pleasing yellow tint. Though not much used, except occasionally in wheelwright work, it is, nevertheless, a good, durable timber. In its localities it is rather difficult of access, and usually other good, time-proved timbers occur, such as E. goniocalyx, E. tereticornis, E. melliodora, E. eugenioides, etc. It does not occur in Tasmania, the tree recorded from that State as this species is quite a different Eucalyptus.

ESSENTIAL OIL. - Leaves and terminal branchlets for distillation were obtained from Barber's Creek, N.S.W., in July, 1898. The yield of oil was 1 per cent. The crude oil was but little coloured, and had an odour resembling those of the cineol-pinene oils. It differed but little in general characters or in constituents from the oil of E. globulus, with the exception that the ester content was higher. It was rich in cineol; pinene was present, but phellandrene was absent. The higher-boiling portion contained the sesquiterpene. Crystallised eudesmol was not detected.

The crude oil had specific gravity at 150 C. = 0.9247; rotation aD + 5.8°, refractive index at 200 = 1.4679, and was soluble in 1 1/2 volumes 70 per cent, alcohol. The saponification number for the esters and free acid was 21.8.

On rectification, 2 per cent, distilled below 1700 C. (corr.). Between 170-183°, 82 per cent, distilled; between 183-224°, 5 per cent, came over, and between 224-270°, 3 per cent, distilled. These fractions gave the following results: -

The cineol, determined by the phosphoric acid method in the first fraction, wes 59 per cent. (O.M.), indicating about 50 per cent, in the crude oil.

Material of this species was also obtained from Lochiel, N.S.W., in September, 1899. The oil was practically identical in composition with the above. The specific gravity of the crude oil was, however, a little less than that of the Barber's Creek sample, but this might be expected from the difference in the time of year; the yield of oil was also greater, probably for the same reason. It was rich in cineol, and was soluble in 1 1/2 volumes 70 per cent, alcohol. This species may, therefore, be considered a good one for commercial oil distillation, and is even better than the oil of E. globulus, as the yield of oil is greater. It would be necessary, however, to rectify the oil before use, because the esters and volatile aldehydes are present in some quantity; but this remark applies to most of the richer cineol oils.

Plate XXV.

Eucalyptus Rodwayi

R.T.B. a H.G.S. Apple Scented or Black Gum

The above samples were mixed together and stored in the dark. In August, 1919, the oil was again analysed. It had not altered much in general characters. Ninety per cent, distilled below 190° C. The crude oil and the rectified portion gave the following results: -

The cineol was determined by the resorcmol method in the rectified portion and calculated for the crude oil; the result was 77 per cent. By the rapid phosphoric acid method (duplicate determinations) the result was 62 per cent, when calculated for the crude oil. Terpineol was detected in the rectified portion. After acetylation the saponification number was only 21, thus showing that bodies other than cineol and alcohols were absorbed by the resorcinol.