16 



The Probable Evolution of the Eucalypts. 



PERHAPS one of the most interesting results brought to light by what appears 

 to us the natural system of classification here adopted, is the affinity shown to 

 exist between the members of the several groups of Eucalypts in their morpho- 

 logical and other physical characters, chemical constituents, venation of their 

 leaves, and the nature of their barks and timbers. And not only is this affinity 

 shown between the species of this important genus, but a close connection is 

 also found to be well marked between Eucalyptus and the cognate genus 

 Angophora, which, therefore, appears to us to be more closely connected to the 

 former both morphologically and chemically than does the allied genus 

 Tristania. 



Since the above was written in 1902, Dr. Cuthbert Hall has published 

 in the Proceedings of the Linnean Society, N.S.W., 1914, and in the Report of 

 the British Association, 1915, the results of his work on the seedlings and 

 cotyledons of a large number of Eucalypts. Photographs are also given. He 

 there shows the close affinity of these two genera in the following words : 

 " The original Eucalypts represented now by those of the E. corymbosa class 

 had large entire reniform cotyledons ; these are practically identical with those 

 of the nearly-related genus Angophora." 



If we deal with the affinity between the Angophoras and the Eucalypts, 

 it will be found that the former have apparently only one feature the absence 

 of a calycine lid which removes them generically from the Genus Eucalyptus. 

 Some Eucalypts, however, show a tendency seemingly to develop petals, for 

 in the case of E. tctrodonta, F.v.M., E. terminalis, F.v.M., E. tessellaris, F.v.M., 

 and a few others, it is found that the calyx is irregularly ruptured, rather than 

 circumcised by a clearly-defined sutural line ; for, as stated by Baron von 

 Mueller in his " Eucalyptographia," under E. tetrodonta, " the strongly-toothed 

 calyx demonstrates some transit towards Angophora, although the lid is in no 

 way dissolved into petals as jn that genus." 



In continuing this connection between these genera, it will be noted that 

 in the nature of the bark, timber, calyx tube, inflorescence, kinos, and particularly 

 in the chemical constituents of the oil, and venation of the leaves, the alliance 

 between certain species is very striking. 



The oils yielded by those Eucalypts known vernacularly as " Bloodwoods," 

 such as E. calophylla, E. corymbosa, E. trachyphloia, E. eximia, &c., and the allied 

 species, E. botryoides, &c., invariably contain a large proportion of pinene ; 

 phellandrene is always absent, and cineol only occurs in traces, if at all. , 



The venation of the lanceolate leaves of all this group of species was found 

 to correspond with that of the leaves of the Angophoras, and this feature is 

 illustrated in plates, i, n, and in. 



It was this affinity in venation which first led us to inquire if the oils, were 

 also in agreement. For this purpose oil was distilled from the leaves of 



