101 



13. TANNIN. 



Tannin is another waste product, and reference has already been made to it in 

 Mr. H. G. Smith's remarks concerning calcium oxalate. 



Most tannins doubtless are waste products, and eventually they are removed through the 

 exfoliation of the bark : similarly, exfoliation rids trees of many other waste products that accumulate 

 in the bark, such as alkaloids, gums, resins, and calcium oxalate. Tannins, because of their bitterness, 

 may be useful incidentally in protecting from animal depredations ; some tannins, known as plastic tannins, 

 probably are of value in nutrition. Tannin production appears to be especially characteristic of 

 xerophytes, desert plants growing in mesophvtie conditions have much less tannin than in their natural 

 habitat. (Coulter, Barnes, and Cowles, op. cit. ii, 72-1.) 



See also " An investigation of the Barks of four Western Australian Species of 

 Eucalyptus." by H. G. Smith. Journ. of Agriculture. Western AustraHa, April, 1905, p. 

 219. This investigation was undertaken to determine the value of these barks for 

 tanning purposes. The species are sahnonophloia. salubris, redunca, and occidental is. 



While some analyses have been made of Eucalyptus barks for tannin, only one 

 variety, perhaps a good species. Eucalyptus occidentalis var. astringens Maiden, the 

 " Mallet " of Western Australia, has been put to commercial use. In this connection 

 see Part XXXVI. p. 143. See also D. E. Hutchins' "A Discussion of Australian 

 Forestry/' p. 239 (1916). 



Mr. C. E. Lane-Poole, Conservator of Forests of Western Australia, is giving 

 attention to the potential value of the tan-bark value of E. platypus and other species. 



The consolidated barks, which include the Gums, and, to a certain extent, the 

 Ironbarks. contain more or less tannin in the form of kino ; the fibrous barks contain 

 it least, in proportion, as the differentiation into fibre has proceeded. 



14. OIL IN BARK. 



A correspondent (Mr. E. H. F. Swain) states that the inner bark of E. acadceformis 

 has a distinct odour of turpentine, and hence the tree is sometimes known as Turpentine. 

 The bark of old trees of E. aggregata contains essential oil. As regards oil in the bark 

 of E. cinerea. see Part XXIV, p. 72. See a paper " On the Essential Oil from the Bark 

 of Eucalyptus Macarthuri," Journ. Roy. Soc. N.S.W., 1, 177, 1916, by H. G. Smith. 

 ' The oil from the bark of this species agrees with that distilled from the leaves. It 

 is equally rich in geranyl-acetate, and need not be kept distinct from the leaf oil." 



There is no doubt that search will bring to light oil in the barks of other species. 



15. FIBRE IN BARK. 



In the Official Record, Intercolonial Exhibition, Melbourne, 1866-67, p. 218, 

 are the results of experiments in paper-making with the barks of E. obliqua, rostrata. 

 amygdalina (radiata). globulus, goniocalyx, corymbosa. leucoxylon, longifolia, Stuartiana. 



