445 



Hppendix H. 



SYSTEMATIC VALUE OF THE CHEMICAL PRODUCTS OF NATURALLY 

 GROWING PLANTS AS AN AID TO THEIR BOTANICAL STUDY. 



It is now generally accepted that, under varying influences of soil and climate, 

 certain cultivated plants may change considerably the character of their chemical 

 constituents, and so develop alterations of a more or less well-defined nature. 



Much of the evidence so far produced in support of this statement, has, 

 however, been derived from cultivated material, and very largely from annuals. 

 A considerable amount of work has already been undertaken in the attempt to 

 arrive at some conclusions in this direction, and MM. Charabot and C. L. Gatin 

 in " Le Parfum chez la Plante," Paris, igo8, have brought together a considerable 

 amount of data bearing on this question, so far as it relates to the alterations in 

 the constituents of the essential oils obtained from certain genera. From the 

 results already formulated they arrive at the following conclusion: — "Toute cause 

 venant influencer la nutrition et par consequent le chimisme d'une plante produit 

 forcement une modification dans la composition de I'huile essentielle qu'elle 

 secrete, . . . mais il est juste d'aj outer que les caracteres anatomiques et 

 morphologiques des vegetaux varient egalement sous les influences qui modifient 

 les conditions de la nutrition, ce qui ne les empeche pas de posseder une valeur 

 systematique." By selection and suitable treatment it has, of course, been 

 possible to increase certain chemical constituents necessary for the successful 

 commercial exploitation of some plants, particularly in the increase of sugar in 

 beet-root. There seems to be no just reason why, corresponding suitable 

 treatment of certain plants should not also increase their oil constituents in 

 the direction of furthering their commercial possibilities. Exhaustive study in 

 this direction would be of considerable value, and possibly rewarded with results 

 of a satisfactory nature. It seems possible that in some such way Nature has 

 already differentiated into distinct species, the members of such large genera as 

 the Callitris and EucalypUis of Australia, because it is to be expected that 

 similar alterations to those which have brought about changes in the chemical 

 constituents of the plant, would also act directly in other directions, and thus 

 cause marked alterations in their morphological characters, such as would be 

 in agreement with these chemical changes. That this is so is demonstrated by 

 the characteristic venations of the leaves of the Eucalypts, which characters we 

 have shown to be contemporaneous with the alterations in the main constituents 

 of their essential oils.* 



Corresponding to these well-marked differences, other changes have also 

 taken place, which have become discernible in the varying barks and woods 

 of the Eucalypts, as for instance, representing the several groups, there are 

 the " Stringybarks," the " Ironbarks," the " Smoothbarks," or " Gums," the 

 " Boxes," the " Ashes," &c. The exudations or Kinos have also varying chemical 

 characters, which are as constant as those of the oils. 



With the Callitris certain changes in morphological characters are also 

 discernible, so much so, that vernacularly the species are distinguished by the 

 people themselves by such terms as " White Cypress Pine," " Black Cypress 

 Pine," " Stringybark Pine," &c., and these distinctive features, we now find, 

 are always accompanied by corresponding alterations in the characters of their 



* "Research on the Eucalypts," Sydney, 1902. 



