323 



/ 73. Eucalyptus citriodora. 



(Hook., Mitch., Trop. Austr., 235.) 

 Citron-scented Gum. 



Systematic. A large tree with a smooth, whitish bark. Leaves lanceolate, 

 up to 6 inches long and 9 lines wide, acuminate, not shining; venation finely 

 marked, lateral veins numerous, oblique, parallel or slightly spreading, intra- 

 marginal vein very slightly removed from the edge, which is more or less irregular. 

 Flowers numerous in axillary panicles. Calyx tube hemispherical to slightly 

 cylindrical, about 2 lines in diameter, pedicel under 2 lines long; operculum 

 hemispherical, umbonate. 



Fruit. Ovoid, truncate, contracted at the edge; 

 rim thin ; valves opening downwards ; 

 under 4 lines in diameter and 6 lines long. 



Only separated with difficulty from E. maculata. 

 Habitat. North coast district of Queensland. 



REMARKS. The above is the locality as at present known of this species. Sir T. Mitchell collected 

 liis specimens far inland, at Beebury Creek, Mantua Downs, and " Sir William Hooker named this Eucalypt 

 (although without flower or fruit) from the deliciously fragrant lemon-like odour, which exists in the dry as well 

 as in the recent state." (Mitch. Trop. Aust. 235.) The term " Citron-scented Gum " is now applied to a Coast 

 tree with a smooth white bark, and is largely cultivated. It is not the only Eucalyptus possessing an aroma of 

 this character in its oil, as this also occurs in the North Queensland " Ironbark," E. Staigcriana, F.v.M. Whether 

 Mitchell's tree is botanically identical with that on the coast and the one to which the name is now applied remains 

 to be proved, for, as stated above, the species was established on the leaves and chemical constituents alone. 



ESSENTIAL OIL. The oil of this species of Eucalyptus consists almost 

 entirely of the aldehyde citronellal, with from 5 to 10 per cent, of other bodies, 

 including a small quantity of ester, a little alcohol, perhaps geraniol or citronellol, 

 and a very small quantity of a terpene. It has no resemblance to that distilled 

 from the leaves of E. maculata. 



This Eucalypt is essentially a Queensland one, growing quite extensively in 

 the Gladstone District, but it readily lends itself to cultivation in other parts, and 

 grows quite well in the Sydney District. The species is quite stabilised, so that 

 the oil always shows comparative constancy, no matter where the trees are grown. 

 It also shows considerable vitality, and we have been informed by a gentleman 

 who knows the district well, that on the Herberton Range to the north 

 of Cairns there are many hundreds of acres where E. citriodora grows plentifully. 

 When he was there the trees had been cut down for mining purposes, but a great 

 quantity of " suckers " had come up, and consequently an abundance of leaf was 

 available. He distilled oil from this material and found it of excellent quality. 



We were unable to obtain leaves from Queensland for distillation purposes, 

 but have investigated the oil commercially distilled there. It was found to be 

 in agreement with the oil we distilled from a. cultivated tree in Sydney. That the 

 constitution of the oil from cultivated trees is similar to that distilled from material 

 growing in its native habitat, can be seen from the results of the analyses we submit 

 herewith, 



