448 



uniform. The morphologically closely agreeing species C. rhomboidca of the coast 

 of New South Wales, was found to cliffer in its chemical characters from those of 

 C. Tasmanica. 



If we consider tlic lime necessar\- for the grnus (\il/itris to ha\'e spread itself 

 over the whole of Australia, it is not difficult to understand why it is that several 

 species have been able to adapt themselves to their environment, and thus to 

 slowly overcome adverse conditions which might have pre\-ented their distribu- 

 tion except in very restricted areas. 



It has been suggested that the various chemical substances found in 

 the vegetable kingdom, such as essential oils, resins, &c., are largely waste products. 

 This supposition, however, does not take into consideration their distribution, 

 alteration, and use in the constructive metabolism of the plant, and the evidence 

 obtained by numerous workers does not seem to support the view that they are 

 waste products. It is more reasonable to suppose that they play an important 

 part in the life of the plant, and assist in the ultimate formation of its several 

 parts. The oleo-gum-resin which forms the greater portion of the latex of Araii- 

 caria Ciinninghamii, certainly does not appear to be a waste product, because of 

 its abundance at any time, and to its continuous formation. In uninjured trees 

 the oleo-gum-resin is rarely found on the exterior, so that if it is not material 

 in a state of transition, one wonders what becomes of it. We have recently found, 

 on severing the branches of a young tree of Tristania conferta, that a small amount 

 of an aromatic oleo-resin exuded from the centre or pith of the severed portion 

 of the trunk. This is interesting for plants of this group, and we are not aware 

 that oleo-resin or resinous products have previously been found in this tree ; so 

 that in this instance the utilisation of this oleo-resin in the construction of the tree 

 is evident, and also that it is quickly used up after it is formed. 



It is shown under Araucaria Cunninghamii that in the formation of the 

 oleo-gum-resin in the latex of that tree, other agents than those supplied by the 

 leaf portion of the plant have evidently been employed, and it would be interest- 

 ing to find out whether this is not largely due to enzyme action. In the formation 

 of the leaf oils in the Callitris the reactions which have taken place appear to be 

 due to reduction rather than to oxidation, because although the alcohol geraniol 

 is present in abundance in some species — C. Tasmanica particularly — yet, no 

 indication of citral, or other oxidised similar product of the alcohols, has been 

 detected in the leaf oil of any Callitris species. In the Eucalypts, oxidised 

 products often occur, and in the oil of some species in large quantities, as citral 

 in E. Staigeriana ; citronellal in E . citriodora; and aromadendral in numerous 

 species allied to the " Boxes.' .M. Emm. Pozzi-Escot (^O.xydases et Reductases, 

 Paris, 1902, p. 51) suggests that the reductases play a considerable part in plant 

 formation, and says: — " On pent dire avec de Rey-Pailhade, que le philothion ou 

 plus exactement les reductases, dans la cellule vivante, sont la porte, on I'une des 

 portes, par lesquelles I'oxygene libre penetre dans I'edifice cellulaire vivant." 



\\'hether this is so or not further researches will disclose, but it seems to 

 us conclusive that the chemical productions of the plant are of such importance 

 in its construction, that for each species peculiarities will eventually arise. The 

 determination of these, wherever possible, should give somewhat exact results, 

 being chemical, and so help towards a deeper knowledge of the peculiarities of the 

 several members of most plant genera. The utilisation of the knowledge thus 

 obtained with both Callitris and Eucalyptus has been of the greatest help in our 

 studies of these peculiarly Australian genera. It seems feasible, therefore, to 

 expect that results of corresponding value would reward similar efforts with other 

 genera peculiar to other parts of the world. 



