BOTANICAL AND CHEMICAL CHARACTERS OP EUCALYPTS. 105 



also a distinguishing feature ; the test is carried out by adding formal- 

 dehyde to the solution (16). Although to the taste and by their 

 behaviour on oxidation with potassium permanganate, the kinos of this 

 group appear to be the most astringent, the affinity of their tannins for 

 hide substance is very slight and the barks of these Eucalypts are of 

 little use for leather manufacture. Eucalyptus species the barks of 

 which can be used commercially for tanning purposes, the ' Mallee,' 

 E. occidentalis, for instance, yield kinos in which Eudesmin and Aroma- 

 dendrin both occur; the tannins of this group have great affinity for 

 hide substance and are rapidly absorbed by it. The kinos of the ' Iron- 

 barks ' and of a few other species are not soluble in alcohol, though 

 readily so in water; they consist largely of a peculiar tannin glucoside 

 which on hydrolysis forms a deep purplish-brown powder having con- 

 siderable dyeing power (17). When these kinos are dissolved in water 

 and alcohol is added in quantity insufficient to cause precipitation, they 

 gelatinise readily when treated "with formaldehyde ; they have little 

 affinity for hide substance and, although plentifully distributed through- 

 out the barks of some species, E. crebra and E. sideroxylon for instance, 

 have little present commercial value. 



A tincture of official strength, made with the kino of E. calophylla, 

 is the best possible of all similar substances for pharmaceutical purposes, 

 because it does not gelatinise in tinctures no matter how long the 

 tincture may be kept, whilst the tannin it contains is highly astringent ; 

 the material can be obtained in very large quantities. E. microcorys 

 would also make an excellent tincture but the kino is difficult to collect. 

 The kino of the ' Eed Gum,' E. rostrata, although official, is not so 

 well suited for the manufacture of tinctures as those already mentioned 

 but may, nevertheless, be considered of fair quality for the purpose; 

 it is also obtainable in some quantity but it is deficient in astringency 

 and is not so resistent to gelatinisation. The exudations of the 

 Eucalypts thus contain substances showing very great variability and no 

 general considerations can be made to fit all the facts. Chemical con- 

 stituents found in the exudations of the members of one group, such 

 as the ' Boxes ' for instance, are not found in those of some other 

 groups. Tannins characteristic of the kinos at one end of the genus 

 have disappeared at the other, astringent bodies of a different nature 

 taking their place. Yet, with all these differences, there is considerable 

 uniformity in progressive alteration, which is in accord with the varying 

 botanical characters exhibited by the members of this large genus. 

 The kinos in which Eudesmin occurs consist largely of catechol tannins 

 and Eudesmin itself is a catechol derivative containing four methoxy- 

 groups in two veratrol nuclei. 



Other Chemical Constituents. — There are a few chemical con- 

 stituents in the Eucalypts which at present do not appear to be closely 

 associated with corresponding botanical distinctive features, as already 

 shown in many specific instances. Perhaps, however, the reason is 

 that sufficient work has not yet been undertaken in the direction of 

 attempting to decide this point. Myrticolorin, the quercetin gluco- 

 side (18), found in such large quantity in the leaves of E. macrorrhyn- 

 cha, is a case in point, as the leaves of some other members of the 

 ' Stringybark ' group do not contain this substance. 



