1. 1 



the gradual alteration <>i the leai venation oi the Genus, which commenced with 

 those species closely associated with the Angophoras. Piperitone is usuall) 

 associated with phellandrene in the oils oi species showing this venation, 

 although its occurrence in some oi them could no1 be decided with certaint} 

 bu1 it is probable thai man} ol the constituents found in these oils are presenl 

 in traces in many ol them. Pinene, also, probably runs through the whole 

 series, <>i course, diminishing more and more as it is replaced by phellandrene 

 or other terpenes. Phellandrene appears to be present in a maximum amounl 

 in the oils ol E. dives, E. Andrewsi, /•.'. radiata, &c, and thesi species show very 

 clearly the characteristic venation for this group In the Lanceolate leaves 

 of these species, too, the marginal vein has receded so fat from the edge that 

 often a second one has commenced to form. In the leaves ol this group, the 

 reticulations between the more prominenl veins in the leaves belonging to the 

 cineol-pinene group have become still more subordinate, and consequently more 

 room is given for the formation of oil glands, and thus the yields ol oil from many 

 species ol this group arc large. The black dots in the photographs show the 

 position of the innumerable oil glands in the leavi The reproduction oi the 



venation can be carried out very successfully by photography, the fresh leaves 

 being used. These are printed directly upon the paper in strong sunlight, and 

 the prints thus obtained can be reproduced by any of the well-known 

 photographic methods. 



In October, iqoi, we read a paper on tins subjeel before the Royal Society 

 -I New South Wales, and demonstrated this alteration of leaf venation in 

 agreement with the chemical constituents, by the aid of a series of lantern slides 

 made from the photographs taken directly from the leaves; the completeness 

 of these can be judged from the reproduction of the leaves in the illustrations 

 (plates i to viu . 



In other parts of this work we show that this alteration in leal venation 

 and chemical constituents is not local in its incidence, and that the specific 

 characters of each species are practically constant over the whole range "! its dis- 

 tribution, and numerous instances are given of this constancy. It can thus be 

 supposed that the formation of the several species "I Eucalyptus has been one 

 of evolution, and that the alteration in the chemical constituents ol the oil has 

 been contemporaneous with the changing of the leal venation. 11 is thus assumed 

 that the several species, as we know them to-day, have gradually de\ iated from a 

 progenitor, and we have attempted to show through which channels this deviation 

 ha taken place. That the constituents of the oil have been' fixed and constant 

 lor a long period of time must he evident by the fad that, to whatever extenl 

 or range any particular specie-, ha- reached, it contains the same characteristic 

 constituents, and has its botanical characters in agreement. This evidence is 

 of the greatesl importance when the length of time is considered which musl 

 sarily have elapsed, before any one species could have established itself 

 over such an extensive area as found to exist to-day. Some Eucalypts, however, 

 appear to possess botanical and chemical characters which give them an affinity 

 with one or two particular specie- only, whilsl a \< w seem to have no pronounced 

 connecting features, and, therefore, appeal to stand quite alone ; such species are 

 thus not easj to place in a regular line ol sequence, as though there were a 

 compL te gradation passing from one species i" another. I In- intermediate forms, 

 then fore, seem to be wanting in several instances, which may, perhaps, he largely 

 a. i ounted lor b\ their extinction, or due to mutation. 



The long period ol quietude or comparativi tability oi terrestrial con- 

 dition-in Australia probably accounts foi the few .indefinite varieties oi Eucalypts 

 wo have met with, and the environment also, having undergone little i ha 



