I9I4-] SOUTHEASTERN NORTH AMERICA. 225 



* 

 must represent an ancestral character of long standing before the 

 evolution of the falcate leaves of the genus with twisted leafstalks 

 and other xerophytic features. 43 



I have dwelt at some length on this question because of its phylo- 

 genetic 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 al- 

 though Myrcia is almost equally old and is certainly closely related to 

 Eugenia. Among the numerous Cretaceous fossils from North 

 America now referred to Eucalyptus there is not a single one that 

 does not exhibit characteristic features of Eugenia or Myrcia, espe- 

 ciallv the latter, a fact greatly impressed on me in handling a large 

 amount of recent material during my study of the Wilcox forms. 



In the Wilcox flora there are six well-marked species of Myrcia 

 and four nearly equally well marked species of Eugenia as well as a 

 single species of Calyptranthes. The latter genus appears also to be 

 represented in recent collections from the Isthmus of Panama. 

 Without pursuing the subject beyond the known facts, confessedly 

 meager, and noting the presence in the Wilcox flora of numerous 

 Combretaceas and a representative of the great tropical family Melas- 

 tomacea, largely American in the existing flora, both of which are 

 families closely related morphologically to the Myrtacese, it would 

 seem that the known facts, as well as the law of probabilities, sug- 

 gest America as the original home of the family. That it reached 

 Europe either by way of Asia or the Xorth Atlantic plateau early in 

 the Upper Cretaceous and became cosmopolitan 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 and to which it has since been so largely 

 confined. The types peculiar to the Australian region represent the 

 relics of the Cretaceous radiation with numerous new types evolved 

 on that continent as Andrews has suggested. This is exactly the 



45 See Deane, H., " Observations on the Tertiary Flora of Australia." 

 Proc. Linn. Soc. N. S. Wales, Vol. 15, 1900, pp. 463-475; Cambage, R. H., 

 "Development and Distribution of the Genus Eucalyptus,'' Presidential Ad- 

 dress, Jour. Proc. Roy. Soc. N. S. Wales. 1913. 



PROC. AMER. PHIL. SOC, LIII, 214. O, PRINTED JULY 14, I914. 



