COMPOSITIOX OF THE FLORA. 



119 



These are the facts of modern distribution. 

 Their interpretation may vary. Andrews,^ 

 from a study of the present distribution, geo- 

 logic climates, and the geologic history of the 

 Australian region, concludes that the Lepto- 

 spermoidetB originated from the Myrtese, and 

 that the Cretaceous forms were widespread, as 

 they undoubtedly were. Before the separa- 

 tion of AustraUa from the Asiatic mainland he 

 believes that the fleshj- fruited forms found 

 tliemselves iji a region of warm, moist climate, 

 but relatively poor soil, and that this edaphic 

 factor was the principal stimulus to the differ- 

 entiation of the Leptospermoideae, which, with 

 the exception of the genus Metrosideros, show 

 adaptations to poor soil and temperate or dry 

 climates, and this exception explains the rela- 

 tively wide distribution of Metrosideros from 

 Asia to the Fiji Islands. The Eucalyptus 

 forms, according to the view of this student, 

 were derived from Metrosideros after the sepa- 

 ration of Xew Caledonia from Austraha and 

 the separation of that continent from Asia. 

 To sup])ort this last point, Andrews is obhged 

 to consider all the (Yetaceous identifications of 

 Eucah-ptus and all the Tertiary identifications 

 outside of Australia as equally misleading. 

 With regard to the presence of Eucalyptus in 

 North America, I think this contention to be 

 not unlikely, for. although in accordance with 

 paleobotanic usage, I have identified numerous 

 forms of Eucalyptus in the North j\jiierican 

 Upper Cretaceous, I have long thought that 

 these leaves represented ancestral forms of 

 Eugenia or Mvrcia, but have hesitated sug- 

 gesting any change in nomenclatuire from the 

 havoc it would play -nath stratigraphic paleo- 

 botany. 



The supposed American Cretaceous fruits of 

 Eucalvptus have long since been shown to be 

 referable to Dammara-hke forms, and in my 

 studies of the Tertiary flora I have scrupu- 

 lously reframed from referi'ing any of the nu- 

 merous m^Ttaceous leaves to the genus Euca- 

 lyi^tus. Regarding the possible occurrence of 

 Eucaly]3tus in Europe. I am not so sure that the 

 identifications of Heer, Unger, and Ettingshau- 

 sen are erroneous. Certain remains considered 

 Eucalyptus fruits seem very convincing from 

 the published figures, and there is not the slight- 

 est doubt that the other great modem Austral- 



'Andrews.E. C, op. eit. 



ian alliance — the Proteaceae — ^was represented 

 in both Europe and America during the Cre- 

 taceous and Tertiary. Tliere is one additional 

 argument against the Cretaceous radiation and 

 the paleobotanic determination of Eucalyj^tus 

 and that is the great persistence of the pecuhar 

 juvenile opposite, cordate, sessile, and hori- 

 zontal leaves, which must represent an ancestral 

 character of long standmg before the evolution 

 of the falcate leaves of the genus with t^visted 

 leaf stalks and other xerophytic featxires.- 



1 have dwelt at some length on this ques- 

 tion because of its phylogenetic importance 

 and the possible bearing of the Wilcox flora on 

 this point. In considering the morphology of 

 the existing species, Eugenia has many claims 

 to be considered the most primitive, although 

 Myrcia is almost equally old and Ls certainly 

 closely related to Eugenia. ^Vmong the nu- 

 merous Cretaceous plant fossfls from North 

 America now referred to Eucalyptus, all with- 

 out an exception, exhibit characteristic fea- 

 tures of Eugenia or Myrcia, especially Myrcia, 

 a fact greatly impressed on me in handling 

 a large amomit of recent material during mv 

 study of the Wilcox forms. 



In the Wilcox flora there are 6 well-marked 

 species of Mvrcia and 4 nearly equally well 

 marked species of Eugenia, as well as a single 

 species of Calyptranthes, which appears also 

 to be represented in recent collections from the 

 Ohgocene of the Isthmxis of Panama. The 

 presence in the Wilcox flora of numerous Com- 

 bretacese and a representative of the great 

 tropical family Melastomatacese, largely Ameri- 

 can in the existing flora, both of which are 

 fa mili es closely related morphologically to the 

 M\Ttaceae, together with other known facts, 

 though confessedly these are meager, as well as 

 the law of probabUities, suggests America as the 

 original home of the family and that it reached 

 Em-ope either by way of Asia or the North 

 Atlantic plateau early in the Upper Cretaceous 

 and became cosmopohtan before the close of 

 the Cretaceous. During the late Tertiary this 

 ancestral stock, which largely coincided with 

 the existing subfamily Myrtoideae, was forced 

 to withdraw from temperate North America to 

 the American Tropics, where it had originated 



- Deane, H., Observations on the Teniaryflora of Australia: Linn. Soc. 

 New South Wales Proe., vol. 15, pp. 463-475, 1900. Cambage, E. H., 

 Development and distribution of the genus Eucalyptus: Pr^idential 

 address: Roy. Soc. Xew South Wales Jour. Proc., 1913. 



