It seems very probable that the effects above described are due to the eucalyptus having such extensive and far-spreading roots, which suck up and appropriate the moisture of the surrounding soil, the presence of which, aided by heat, giving rise to vegetable decomposition, is believed to be the cause of malarial poisoning.
The avidity of the plant for water is very great; it has been computed that one tree will absorb ten times its weight of moisture from the soil.[285] It is most likely owing, at any rate in very large measure, to this cause, rather than to the supposed antiseptic and disinfecting odours exhaled by its leaves, that the salubrious effects of the eucalyptus are due. The blue gum tree, or Eucalyptus globulus (so distinguished because of the rounded form of the lid which covers its unexpanded flower bud), has been successfully introduced into Asia,
Africa, and Southern Europe. If, as asserted, it can only exist in a climate where the temperature is never lower than the freezing point, its domestication (save in hot-houses) is impossible in our own country.
[285] ‘Pharm. Journal,’ February 5th, 1876.
Eucalyptus Globulus (from the ‘Archiv der Pharm.,’ 1873, p. 129.)
The Eucalyptus globulus is a very rapidly-growing tree, and attains to great proportions. “In some cases it has been known to attain the colossal dimensions of 350 feet in height and a 100 in circumference.”[286]
[286] Bentley.
This magnitude is entirely out of proportion to the size of the seed, which is very minute; so minute that it has been computed one pound weight of the seed could produce 162,000 trees. Various preparations of the leaves and
bark of the eucalypti have been introduced into medicine, which will be found under the respective pharmaceutical preparations. They were asserted to be specially serviceable in intermittent fevers and bronchitis. The idea that their efficacy in the former class of disease was due to the presence in the barks of the eucalypti of an alkaloid similar to, if not the same as, quinine, has been shown to be an erroneous one, from the experiments of the Government chemist of Ootacamund (Mr Broughton), who, after a most careful chemical analysis, failed to discover either quinine, quinidine, cinchonine, cinchonidine, or the least trace of any one of the cinchona alkaloids.