It can also be demonstrated with other Eucalyptus species that the formation of their characteristic odoriferous constituents commences very early in the life history of the plant, and remains persistent throughout its whole growth. In the very early leaves of the seedlings of E. citriodora, for instance, the citronellal odour of the oil of this species can readily be detected, and this is also the case with other Eucalypts,. the oils of which have a sufficiently distinctive odour.

In the gardens around Sydney trees of E. citriodora have been planted for ornamental purposes, and they grow very well in the Sydney soil and climate; but we know of no systematic attempt to cultivate this species for oil production. The investigation of the oil from the Sydney grown material showed it to be identical in general characters with that distilled from trees growing naturally in Queensland.

All the oil of E. citriodora, so far commercially obtained, has been distilled from trees in their native habitat, and as the species grows to a large size the difficulty of obtaining leaf material for distillation by lopping off the branches is apparent, although this method is followed to a considerable extent.

Plate CI.

Eucalyptus Citriodora

Climbing a tree, in order to procure leaves for distillation.

The accompanying photograph (Plate CI) shows the operator climbing the long, straight stem of the tree for the purpose of lopping off the branches in order to collect the leaves, and illustrates this laborious procedure very well. A tree of the same species is seen on the left of the picture.

The yield of oil from E. citriodora from naturally grown material is about 07 per cent. for leaves and terminal branchlets, and the product is in considerable demand and sells at a high price. The species thus gives promise of success if it were systematically cultivated, and it is evident that it must be more satisfactory to collect the material for distillation from cultivated plants than from big trees.