The object of this was to ascertain, from material belonging to well-detined 

 species, the influences of locality, soil, and climate, on the chemical constituents 

 of the tree. It has been advanced by some writers that these have considerable 

 action upon plants generally, and that, therefore, constancy of results could 

 hardly be expected. 



Our researches on the oils of the Eucalypts showed a remarkable constancy 

 in the chemical constituents of indi\'idual species of that genus. With the oils of 

 the Callitris the same practical uniformit}' of constituents exists, although not so 

 markedly as with the Eucalvpts, as the rotation figures show more variation. 



The distillation of the leaves and terminal branchlets was, in most cases, 

 continued for six hours, as it was found that a fair quantity of oil came over during 

 the fifth hour. The difficulty of obtaining the oil from the leaves by steam 

 distillation appeared to be due to the hidden nature and position of the oil glands, 

 as shown in numerous illustrations. The structure and contour of these may 

 also be seen from the microphotographs of the leaves under the several species. 

 The distillations were carried out on material collected similarly to what would 

 be done in practice, so that the yield of oil obtained with each species may be 

 taken as the commercial one. C. intratropica is the only exception, as with this 

 material most of the coarser branchlets had been stripped. 



The crude oils were usually but little coloured, due to the fact that the 

 amount of free acid in the terpene oils was very small indeed. Those oils contain- 

 ing an increased amount of esters were usually darker in colour, and the free acid 

 was more pronounced. On keeping these oils, the slow alteration of the geranyl- 

 acetate caused them to become even more acid. When redistilled under atmos- 

 pheric pressure, the esters partly decomposed at the temperature required, with 

 the separation of a portion of the acetic acid, but for comparative purposes this 

 had little influence on the results. The oils were all colourless when redistilled, 

 or when purified by steam distillation. 



Xo indications were obtained in any of the oils for either sylvestrene, 

 phellandrene, or cineol. The leaf oil of one species, Callitris Macleayana, contained 

 a hydrocarbon, most probably belonging to the C,„H,^ series, and when isolated 

 in as pure a condition as possible, by fractional distillation, it resembled ordinary 

 menthene, both in odour and appearance. The physical properties of the oil of 

 this species were distinctly different from those of the oils of the other species of 

 Callitris, due evidently to the presence of an increased amount of this constituent 

 in the oil, and which reduced the specific gravity of the crude oil considerably. 

 We have isolated a hydrocarbon of the C,„H,„ series from the latex of Araucaria 

 Cimninghamii (see under that species in this work), and in which material a member 

 of the C,„H„ group probably also occurred. The resins isolated from the latex 

 at the same time, strongly resembled the sandarac resins from the Callitris ; 



