94 



LOWER EOCENE FLORAS OF SOUTHEASTERN NORTH AMERICA. 



coiTolati'd with iiioilcni arid coiulitious, should 

 have really been developed in these early floras. 



The genus luga, represented in the Wilcox 

 hy 4 well-marked species, includes more than 

 1.50 species in the existing flora, all df which 

 are confined to the American tropical and 

 subtropical regions. Its geologic history is 

 largely unkjiown, although it appears to he 

 represented in American Upper Ci'etaceous 

 floras by Inga cntacea Lesquereux, which 

 occurs m the Dakota sandstone and in the 

 Tuscaloosa fonnation of Alabama. Ettings- 

 hausen has tlescribed a species from the 

 Cenomanian of Saxony {Inga cottai) ; the Euro- 

 pean Miocene has furnished 2 or 3 species; and 

 Engefliardt has describeil a Tertiary species 

 from Bolivia. 



The genus Pithecolobium, which belongs to 

 the same tribe as Inga (Ingese), is represented 

 by 2 Wilcox species. Most of the 100 or more 

 existing species are American, more than a score 

 live in tropical Asia, and a few are found in 

 tropical Australia and Africa. With the ex- 

 ception of a Tertiary' species from Bolivia, I do 

 not know of other fossU occurrences. 



The genus Mimosites, which includes 4 

 Wilcox species, represents trees of the Mimosa 

 type that are very abundant in recent species 

 referred to several genera, either American, 

 Asian, Australian, or African, and abundantly 

 represented in European Tertiary floras. Its 

 Cretaceous ancestry is hidden among the 

 species of leaflets referred to the form genus 

 Leguminosites. The genus Mimosa, which is 

 apparently most like the Wilcox Mimosites, 

 includes more than .300 existing species, chiefly 

 confined to the wamaer parts of America, 

 although they are represented in Asia, Africa, 

 and Australia. 



Except for the family Lauracese the Ct^sal- 

 piniacese, which contains 26 species, is the 

 largest family in the Wilcox flora and it is 

 certauily a fact of considerable interest that 

 the massing of the modern species in the 

 American Tropics shoidd be foreshadowed by 

 their abmidance on this Continent as early as 

 the lower Eocene. 



The Wilcox genera are 5 in number, of which 

 the largest is Cassia, which includes 12 species. 

 Cassia is the largest Wilcox genus except 

 Ficus, and aU of its species find their modern 

 counterparts in existing, species of tropical and 

 subtropical America, many of which are men- 



tioned by nanie in the systematic part of this 

 work. Numerous as are the Wilcox species of 

 Cassia there was apparently greater specific 

 difi^erentiation in contemporaneous European 

 deposits, since Ettingshausen records 15 species 

 in the flora of Alum Bay (Ypresian of Isle of 

 Wight). Cassia has between .300 and 400 

 existmg species, found in the wanner temper- 

 ate and tropical regions of all the continents 

 and especiaUy aV)undant in tropical America. 

 Then- place of origin is miknowni, since thej' 

 make their appearance in the Upper Creta- 

 ceous almost simultaneously m New Zealanil, 

 Australia, Bohemia, Saxony, Greenland, the 

 Atlantic Coastal Plain, and the Dakota sand- 

 stone of the Rocky Mountain province. More 

 than 100 fossU species are already known. The 

 Eocene distrilmtion sheds no light on the early 

 history of the genus, for species occur in such 

 widely separated regions as North America, 

 Europe, and Australia. There are numerous 

 Oligocene and Miocene species, the Oligocene 

 records being ccmfhied to Europe and Africa 

 and the Miocene records being confined to 

 Europe and North America. C.issia Wiis 

 abundant along the shores of the Pliocene 

 Mediterranean of Europe, and 4 species are 

 recorded from South American beds which are 

 thought to be of Pliocene age. Pleistocene 

 species are recorded from Maryland, and also 

 from the East Indies (Java), where they are 

 associated with Pithecanthroims eredus Du])ois. 

 One fact is certain — the genus has been a part 

 of the American flora since the dawn of the 

 Upper Cretaceous, and several of the Wilcox 

 species are the undoubted prototypes of 

 existing forms of tlic American Tropics. 



The genus Cercis, which includes a single 

 Wilcox species, makes its first recorded ap- 

 pearance in geologic history in the Wilcox 

 species, in the 3 species recorded from- the Fort 

 Union formation of the Rocky Mountain prov- 

 ince and in a species found in the Ypresian of 

 the Paris Basin, so that its appearance was 

 practicaUy contemporaneous in France and 

 Tennessee. It continues on both continents 

 down to the present, being even represented 

 in the Pleistocene of both regions. The mod- 

 ern species number 5 or 6 and inliabit th" 

 warmer temperate regions of /Vmerica, Europe, 

 and Asia. 



There is one species of Ciesalpinia in the 

 Wilcox and it is almost identical in character 



