349 



Average Yields of Oil from the Several Species 

 of Eucalyptus included in this work. 



CONSIDERED broadly the variation in the amounts of oil obtainable from the 

 leaves of any particular species of Eucalyptus depends largely on the season and 

 on the condition of growth of the material employed. In times of drought the 

 secretion of oil appears to diminish, or else it is used up in the struggle for existence, 

 but after an abundance of rain the trees soon again yield the normal amount of oil. 



Under ordinary conditions the larger quantity occurs in the spring and 

 early summer, when the growth is more vigorous, falling again during the winter 

 months, and with most of the cineol oil-producing species the product becomes 

 correspondingly richer in that constituent as the oil decreases in amount. Not 

 only is this the case with the oil while in the leaf, but even after extraction an 

 increase in cineol has been observed, more particularly with oils derived from 

 species belonging to one well-defined group. Several instances of this increase in 

 cineol after extraction will be found recorded in this work. 



The identity of the constituent responsible for this alteration is not at 

 present clear, although the change is apparent mostly in those oils in which the 

 formation of the insoluble deposit has been observed. This question is more 

 fully considered in the article dealing with this deposit. 



The increased yield is usually associated with an increase in the terpenes 

 characteristic of the oil of the species, as pinene in the pinene-cineol oils, phellan- 

 drene and pinene in the phellandrene-pinene-cineol oils ; and phellandrene in the 

 phellandrene-cineol oils. 



The yield of oil from the " suckers " or adventitious shoots is, with many 

 species, greater than from the mature lanceolate leaves, and in some cases this 

 increase is considerable. The constituents characteristic of the oil of a particular 

 species are, as a rule, also those of the product from the abnormal growth, a 

 fact of considerable economic importance. 



In a paper (Proc. Roy. Soc. Vic. XII, 10, and Pharm. Journ. 3, 5, 270), 

 Mr. Bosisto deals with the problem, whether the Eucalyptus is a fever-destroying 

 tree. In this paper he calculates the probable amount of oil in gallons existing 

 in these trees over a large area of country at any one time. But when we 

 consider the varying amounts of oil contained in the leaves of the severa.l species 

 such approximations must be merely guesses. By referring to the table of yields 

 it will be seen that the oil obtainable from the various species ranges from 3.5 per 

 cent, down to practically nothing; so that without a fair approximation of the 

 extent or range of the various species is determined, it appears hopeless to 

 attempt to solve the problem of available supply by this method. That it is 

 practically unlimited in Australia we readily admit, and also that cineol oils con- 

 forming to the British Pharmacopoeia standard can be produced in any quantity 

 required. This statement is also true for the phellandrene oils. It cannot but 

 be observed what a great variety of oils are obtainable from the several Eucalyptus 



