222 BERRY— LOWER EOCENE FLORA OF [April 25, 



to Australia. Sassafras has well-marked foliar characters of both 

 form and venation that render it readily recognizable in the fossil 

 state. Upwards of two score fossil forms have been described. The 

 oldest of these are three well marked species in the Patapsco forma- 

 tion (Albian) of the Middle Atlantic slope in Maryland and Vir- 

 ginia. A species is recorded from this horizon in Portugal but the 

 identification is very doubtful as is that of a Cenomanian species 

 described from Bohemia, which latter probably represents the genus 

 Sterculia. In America on the other hand the genus is widespread 

 and well differentiated at the base of the Upper Cretaceous, rang- 

 ing from Greenland along the coast and in the interior to South 

 America and with about a dozen known species. By Eocene times 

 Sassafras had reached Europe 43 probably by way of the Arctic 

 regions, where it has been found throughout the Oligocene and Mio- 

 cene. In the Pliocene the European forms had retreated southward 

 but remained common in Italy, France and Spain. The glaciation of 

 the Pleistocene caused their extinction on that continent, the single 

 existing species surviving today in the original home of the genus. 



The order Myrtales as developed in the Wilcox flora contains 11 

 species of Myrtacese, 9 species of Combretacea?, 1 species of Trapa- 

 ceae and 1 species of Melastomacese, as against over 7,000 species 

 in the existing flora. 



The family Myrtacea? has over 3,100 existing species separated 

 by taxonomists into 2 subfamilies. The first of these the Myrtoide?e 

 with 32 genera and about 2,400 species comprises mostly tropical 

 forms of which over 75 per cent, are confined to the western hemi- 

 sphere. There are over 200 in Asia, one of which extends into 

 southern Europe, about 75 in Africa, about 200 in Australia, and 

 about 60 in Oceanica. Nineteen of the genera are confined to Amer- 

 ica and these include the only monotypic genera in the subfamily, three 

 in number, as well as large and greatly differentiated genera like 

 Myrcia with upwards of 450 species. The two other large genera, 

 Myrtus with 178 species and Eugenia with about 1,300 species, are 

 the only two genera found on all the continents and in these two 

 genera America furnishes [35 species of Myrtus and 850 species of 

 Eugenia, or over 60 per cent. The second subfamily, the Leptosper- 



43 A very doubtful form is recorded from Australia. 



