140 BERRY— LOWER EOCENE FLORA OF [April 25, 



meager, trees increase in passing toward the equator. For example 

 the state of Maryland which is in latitude 38° to 39° 30' is in effect 

 a cross section of the Coastal Plain, Piedmont Plateau and the Alle- 

 ghany Alountains with great differences of climate, topography and 

 soils. It is moreover the meeting ground for plants of northern and 

 southern range. In spite of these facts there are only about 150 

 arborescent forms in its flora. On the other hand in Small's recently 

 published Trees of Florida (1913) there are 366 native and natu- 

 ralized arborescent forms, and if Florida furnished much altitudinal 

 variation the number would be much larger. For example the ar- 

 borescent flora of the Philippine Islands includes 665 native species 

 and many additional introduced forms. Even remote oceanic islands 

 if of sufficient size and topographic variety to overcome the adverse 

 action of winds have a large arborescent flora. Thus the Sandwich 

 Islands have 225 native species of trees distributed among 45 families, 

 the larger being the Rutacese (32 species), Rubiaceae (31 species), 

 Campanulacese (15 species), Araliacese (14 species), Pittosporace?e 

 (12 species), Palmacese (11 species), Myrsinacese (11 species), and 

 Malvaceae (10 species).^ 



The general physical conditions of a remote geological epoch may 

 be more or less completely deduced in advance from the character of 

 the sediments : the run-off from the land can be approximated and 

 consequently the altitude of the land and the probable rainfall as well 

 as any periodicity in these factors. These are all reflected in the 

 sediments. Work like that of Vaughan* on the deposits of the 

 Florida Keys or that of Drew^ on the part played by denitrifying 

 bacteria in the formation of limestones, enables a careful paleobota- 

 nist to in a measure predict the character of the flora that clothed the 

 marginal lands. In deposits that teem with the remains of marine 

 life as do many of the Tertiary formations of southeastern North 

 America it is possible to arrive at very close approximations of the 

 actual temperatures of the coastal waters. It may be safely assumed 

 that boreal or temperate floras did not flourish in proximity to trop- 



3 Rock, J. F., " The Indigenous Trees of the Hawaiian Islands," Hono- 

 lulu, 1913. 



* Vaughan, T. W., Carnegie Institution, Publication 133, 1910. 

 ° Drew, G. H., Yearbook, Carnegie Institution, No. 10, 1911. 



