208 SECTIONAL ADDRESSES. 



studied so successfully at East Mailing, Long Ashton and Merton ; or 

 with cacao, which is engaging the attention of botanists and agriculturists 

 in Trinidad, Ceylon and the Gold Coast. 



A similar problem, where the systematic botanist requires the assistance 

 of his economic colleague, has recently been investigated in Australia by 

 Messrs. Penfold and Morrison of the Technological Museum, Sydney.^* 

 This concerns the oil yielded by Eucalyptus dives Schseur. 



E. dives is a species easy of botanical determination, and is of economic 

 value for its oil, which has a piperitone content of about 45-50 per cent. 

 which is used for the manufacture of thymol and menthol. The recently 

 increased demand for synthetic thymol and menthol has led to fresh areas 

 being exploited, and oil has been obtained yielding only 5-15 per cent, of 

 piperitone — morphologically, however, the trees were true E. dives — while 

 some other trees, which Australian botanists referred unhesitatingly to 

 this species, contain oil with under 5 per cent, piperitone and 45-75 per 

 cent, cineol. It might be thought that ecological conditions are concerned 

 in these striking difierences — for a typical form and three distinct physio- 

 logical varieties have been recognised by their oil characters — but near 

 Goulbourn, N.S. Wales, the type form with 40-50 per cent, piperitone has 

 been found growing alongside the variety B, containing only 10-20 per 

 cent, piperitone with 25-50 per cent, cineol. The latter form is of no 

 commercial importance, and it was because oils with a low percentage of 

 piperitone were coming to the distillers, who therefore supposed the oil had 

 been adulterated, that these physiological varieties came to be detected. ^^ 



Here, then, is an interesting piece of investigation which brings the 

 botanist into alliance with the chemist. 



A similar problem exists with regard to camphor, where, as is well 

 known, two, and perhaps more, physiological varieties exist in the species 

 Cinnamonium C amphora, which botanists are unable to separate. In the 

 one case solid camphor is yielded on distillation, in the other camphor 

 oil ; and it is even stated by the Japanese authorities in Formosa that 

 from one side of the stem of a tree solid camphor may be obtained, while 

 the other side yields only oil. Whether this be true or not, it is the fact 

 that the valuable economic tree is that which yields solid camphor, and 

 that in our Colonies, especially in Mauritius, practically all the trees 

 are oil-yielders, and therefore well-nigh valueless. 



Since this is a matter of considerable economic importance, it has seemed 

 desirable to test whether climatic or other conditions in any way influence 

 the character of the product, and in the hope of solving the question layers 



1^ The Occurrence of a number of Varieties of Eiicalyptus dives as determined by- 

 Analyses of the Essential Oils, Part I, 1927, Part II, 1928— A. R. Penfold and F. R. 

 Morrison, Journ. dh Royal Society, N.S.W., Vol. Ixi. and IxLi. 



1' Messrs. Penfold and Morrison consider that the varieties, between which there 

 are intermediate forms, may be classed as follows : — 



1. E. dives, Type . Piperitone 40-50 per cent., Phellandrene 40 per cent. 



2. Var. A . . Piperitone 6-15 per cent., Phellandrene 60-80 per cent. 



3. Var. B. . . Piperitone 10-20 per cent., Cineol 25-50 per cent., together 



with Phellandrene. 



4. Var. C. . . Cineol 45-75 per cent., Piperitone under 5 per cent., Phel- 



landrene absent or present in small quantity only. 

 Only the Type and Variety C are of commercial importance. 



