144 BERRY— LOWER EOCENE FLORA OF [ApHi 25, 



phyta which are such a preponderating element in all fossil floras up 

 to the Middle Cretaceous are represented by a doubtfully determined 

 Lycopod and six species of ferns. 



Ferns are among the most abundant (in specific differentiation) 

 vascular plants in the flora of tropical America, the island of Jamaica 

 being especially celebrated for its fern flora. Grisebach enumerated 

 340 species of ferns in his " Flora of the British West Indies " pub- 

 lished in 1864. In Urban's more recent work 182 species of the 

 Polypodiacese alone are recorded from Porto Rico. The following 

 five genera have been recognized in the Wilcox: Aneimia, Lygodiuni, 

 Asplcnkun, Pteris and Meniphylloides — each represented by a single 

 species except the genus Aspleninm which has two species. While 

 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 an extensive flora is preserved in the pipe-clays. The 

 explanation of this seeming disparity between the fern representation 

 in the Lower Eocene and in modern floras is readily formulated and 

 it will also indicate the reasons for thinking that the real Wilcox fern 

 flora if it were available for study would be a rich and varied one, 

 comparable at least with the existing fern flora of the lowlands of 

 subtropical America. 



The known Wilcox flora is almost entirely a coastal flora made 

 up very largely of strand types. Very few elements in it can be 

 legitimately considered as derived from inland areas by stream trans- 

 portation, in fact their condition of preservation alone proves that 

 they grew in the immediate vicinity of 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 example the majority of the Jamaican ferns are found on the 

 Blue Mountains. The most striking exception to this statement is 

 the genus Acrostichum which strangely enough has not yet been 

 positively recognized in the Wilcox flora although it was widespread 

 along the shores of the Mississippi Gulf in the succeeding Middle 

 Eocene (Claiborne) and Lower Oligocene (Vicksburg) floras, as 

 abundant apparently as it is in the existing flora of tropical tidal 

 marshes in both the Eastern and the Western Hemispheres. Another 



