74 



LOWEK EOCliXE FLORAS OK HOUTilEASTEKN XOliill A.MEIUL'A. 



Ill oomparisoii with foreign Eocene iloras of 

 similar ajre it maybe noted that Ettingshausen 

 enumerated 72 genera and 200 species from the 

 London chiy of the Isle of Shei)pey' and 116 

 genera and 274 species from Alum Bay, on the 

 Isle of Wight.- I mention these two English 

 floras specificalh-, because though never ade- 

 cjuately described they are at least partly 

 contemporaneous with that of the Wilcox, as 

 I hope to show in the chapter on correlation, 

 and they therefore offer interestmg details for 

 comparison, as will subsequently appear. 



The Wilcox flora comprises 1.'34 genera in 63 

 families and 37 orders. The Thnllophyta are 

 represented by a few species of leaf-spot fungi, 

 but if the student were to follow the fashion 

 set by the older Em'opean paleobotanists the 

 so-called species of spot fungi could be increased 

 many fold, for I hava only picked out for enu- 

 meration certain conspicuous or characteristic 

 types. The Bryopliyta, as is the rule in fossil 

 floras, are entirely um'e presented, although the 

 sediments in many places would have pre- 

 served them in perfection if they had been 

 present, and the assumption is logical that they 

 were either confined to more northern latitudes 

 at this time or were an exceedingly minor ele- 

 ment in the flora. The Pteridophyta, which 

 are such a preponderating element in all fos- 

 sil floras up to the middle Cretaceous, are rep- 

 resented by a doubtfully determined lycopod 

 and six species of ferns. 



Of the vascular plants in the flora of tropical 

 America, ferns are among the most abundant 

 in specific differentiation, those of the island of 

 Jamaica being especially numerous. Grise- 

 bach enumerated 340 species of ferns in his 

 "Flora of the British West Indies," published 

 in 1864. In Urban's more recent work 182 

 species of the Pol^-podiaoefe alone are recorded 

 from Porto Rico. Tlie five genera Aneimia, 

 Lygodium, Asplenium, Pteris, and Meniphyl- 

 loides have been recognized in the Wilcox, 

 each represented by a single species, except the 

 genus Asplenium which has two species. 

 Though six species seems a small number of 

 ferns in a subtropical flora like that of the 

 Wilcox, it is just twice as many as have been 

 found in the contemporaneous deposits of Alum 

 Bay on the Isle of Wight, where the remains of 



1 Ettingshausen, C. von, Roy. Soc. London Proc, vol. 29, pp. 38S-396, 

 1879. 

 > Ettingshausen. C. von, itlem, vol. 30, pp. 228-236, 18S0. 



an extensi%-e floi-a are preservcnl in tlus pipe 

 clays. The explanation of this seeming dis- 

 parity between the abundance of the ferns in 

 the lower Eocene and in the modern floras is 

 readily formulat(Ml and it also indicates the 

 reasons for thinking that the Wilcox fern flora 

 if it were available fur study would be z'ich and 

 varied, comparable at least with the existing 

 fern flora of tlie lowlands of subtropical 

 America. 



The known Wilcox flora is almost entirely a 

 coastal flora, made up very largely of strand 

 ty]Des. Very few elements in it can be properly 

 considered as derived from inland areas by 

 stream transjiortation. In fact the conditioii 

 of preservation of most of the plants proves 

 that they grew in the immediate vicinity of the 

 places where they are now found as fossils. 

 With a few striking exceptions the existing 

 tropical and subtropical fern floras are floras of 

 humid inland or upland habitats. For exam- 

 ple, most of the Jamaican ferns are found on the 

 Blue Mountains. The most striking excep- 

 tion to this statement is the genus Acrosti- 

 chum, which strangely enough has not yet been 

 positively recognized in the Wilco.x flora, al- 

 though it was widespread along the shores of 

 the Mississippi Gulf in the succeeding middle 

 Eocene (Claiborne) and lower Oligocene (Vicks- 

 burg) floras, as abundant apjjarently as it is 

 in the existing flora of tropical tidal marshes 

 in both the Eastern and the Western hemi- 

 spheres. Another fern typo likely to appear in 

 coastal thickets is the genus Lygodium, of 

 scandent habit, and this genus is represented 

 in the Wilcox flora by both sterile and fertile 

 fronds. It is likewise common in the Claiboi'ne 

 and Vicksburg floras and in Tertiary floras gen- 

 erally. Beside Lygodium the family Schizse- 

 acese is represented by a species of ^\jieimia, 

 which must also be considered to have been a 

 coastal ty[3e in the early Eocene as are some 

 of its species at the present time, since very 

 similar species of Aneimia are found in a large 

 number of Eocene coastal deposits both in this 

 country and abroad. 



The remaining four species of Wilcox ferns 

 are all rc^ferable to the family Polypodiaceie, 

 which is the dominant existing family of the 

 fern phylum. The two species of Asplenium 

 are types readily matched by existing Central 

 American species. The Pteris, not certainlv 

 identified as a true species of this common 



