14 
OILS AND KINOS. CLASSIFICATION. 
(d) Other Uses—Certain of the oils are used m manufacturing s °fps> 
ants, and solvents, with the prospect of an indefinite numbei of other uses. 
The usually ruddy substance that exudes from the stems and iarge branches 
of many Eucalyptus trees is commonly called gum, and was r^oni 
trees themselves being called gums; but it must not be confused with aca g 
or with the inflammable resins obtained from many conifers. tt ls a k ' no c 
sisting largely of tannin and other substances. In medicine it selves as 
"Sr„ge,,t 8 .id in the art, for v.rious purser. Some “U^e l„ge 
quantities of kino; others only a little; and some none at all ^e “Piousness 
of the exudation appears to depend to some extent upon local conditions of soil 
and climate. The presence or absence of kmo should always be noted when we . 
studying a Eucalyptus tree in the bush. 
By the aid of these determining factors botanists have made out “d recorded 
about 400 species of this wonderful genus. The task has been difficult and slow 
and as there is much unexplored country, many species may still remain to» bedi. 
covered and described. Some species were easily separated from all othei. y 
their distinctive and peculiar characters; but groups were found with foliage and 
inflorescence so nearly alike that the greatest care was needed m coming to con¬ 
clusions about them. Even when types had been settled there remained inter¬ 
mediate forms the right placing of which required the most patient and accuiate 
research. Some of these intermediate forms are now regarded as hybrids and are 
so treated and discussed by J. H. Maiden in Volume VI. of his Critical Revision. 
CLASSIFICATION. 
One of the greatest aids to the acquisition of knowledge is classification or 
grouping. If the grouping is based on affinity or near kinship in the units and sub- 
groups, and is therefore natural and orderly, we can compare one group wit i 
another. Judgment and memory are assisted, and progress in mastering the truths 
before us is rapid and permanent. Complaint has often been made that writers on 
the genus Eucalyptus have not been able to agree upon any scheme for classifica¬ 
tion of the species. The failure to agree has not been due to any lack of learning 
or industry on the part of the writers, but to the inherent difficulty of the subject. 
The genus is very ancient, and its ramifications are both highly evolved and widely 
distributed. Affinity is obvious in some cases, but bafflingly obscure in very many 
others. All the great writers have felt the need for classification, and each has 
wrestled with the problem in his own way. Bentham, with great ability and 
research, suggested a scheme based on the shape and mode of opening of the anthers. 
Mueller modified Bentham’s scheme but did not adopt it. He himself outlined a 
scheme having regard to the texture and appearance of the external bark on 
mature trees, but he did not follow it in arranging his Eucalyptographia. One 
hundred species are there described in ten decades, and the species in each decade 
are arranged alphabetically. Messrs. Baker and Smith based a scheme on the 
chemical analysis of the essential oils; but they did not include all the species, 
nor did they make it appear certain that oil analysis would sufficiently agree with 
other tests of affinity to form a basis for complete grouping. J. H. Maiden, finding 
all proposed schemes incomplete and unsatisfactory, adopted in the earlier 
