72 



LOWEE EOCEKE FLOBAS OF SOUTHEASTERN ^'ORTH AMEEICA. 



CHARACTER AND ECOLOGY. 



COMPOSITION OF THE FLORA. 



It is of vittd iinportauce that the determina- 

 tions made in the present study rest on real 

 and not fancifid affinities, for the conchisions 

 jiresented as to chmatic and other physical 

 conditions are largely dependent on tlie cor- 

 rectness of the identifications. I fiillj'' realize 

 that the statistics given under this heading 

 are by no means complete, but I believe that 

 even the imperfect survey here given will be 

 of value not only to paleobotanists and geolo- 

 gists, but to botanists and others interested in 

 the history and the geograpliic distribution 

 of the higher plants. The problem is not 

 so intricate or so insoluble as it might seem 

 to a student who is strongly impressed by 

 the thousands of living and extinct genera- 

 De Candolle estimated that the living flowering 

 plants included about 250,000 species, and if 

 to tliis number be added the herbaceous species 

 living in recent geologic times the number 

 would be enormously increased. The ratio of 

 arborescent to herbaceous types was much 

 gi-eater in the Tertiary period than it is now 

 and the trees were probably more abundant 

 and varied than in the existing flora. They 

 certainly were in all Tertiary floras outside the 

 Torrid Zone, as is sho\vn by the Eocene floras 

 of North America, the Miocene floras of Europe, 

 or, to cite an extreme case, the Tertiary floras 

 of the Arctic and Antarctic regions. 



Though the arborescent flora of tlie Tem- 

 perate Zone is relatively meager the number of 

 species of trees increases toward the Equator. 

 Maryland presents a cross section of the Coastal 

 Plain, Piedmont Plateau, and Allegheny 

 Mountains, regions which exhibit great differ- 

 ences in cfimate, topography, and soils, and is 

 the meeting ground for plants of northern and 

 southern range, yet it contains oidy about 150 

 species of trees. On the other hand, Small's 

 "Trees of Florida" (published in 1913) lists 

 366 native and naturalized arborescent forms, 

 and if Florida exliibited gi'eater variation in 

 altitude the number would be much larger. 

 The trees of the Phifippine Islands, where the 

 range in altitude is much greater, include 665 

 native species and many additional introduced 

 forms, or more than 10 per cent of the esti- 

 mated totid number of species of flowering 

 plants in the Philippine flora. Even remote 



oceanic islands, if suificienfly large and shel- 

 tered by topograpliic features from the adverse 

 action of winds, have a large arborescent flora. 

 Thus the Hawaiian Islands have 225 native 

 species of trees, distributed among 45 families, 

 those having the greater number of species 

 being the Eutacete (32 species), Rubiacefe (31 

 species), Campanulacefe (15 species), Aralia- 

 ceag (14 species), PittosporaceiB (12 species), 

 Palmacefe (11 species), Myrsinacero (11 species), 

 and ^lalvacete (10 species).' 



Koorders collected 700 species of trees in the 

 Celebes during a visit of four months. He also 

 says that he has specimens of about 1,200 

 ai'borescent species indigenous to the island of 

 Java, or about 25 per cent of the total num- 

 ber of flowering plants in the flora of that 

 island. In an area of only 3 square kilometers 

 on the small island of Kambangan, off the 

 Javan coast, Koorders collected 600 species of 

 trees that illustrate not only the wonderful 

 abundance of arborescent forms in the Tropics 

 but the mamier in which um-elated species are 

 mixed, so that pure stands, such as we see in 

 the coniferous forests of the Temperate Zone 

 and also in part in the deciduous forests, are 

 unknown in tliose regions. 



The general physical concUtions of a remote 

 geologic epoch may be more or less completely 

 deduced from the character of the sediments. 

 The approximate run-off from the land and 

 consequently the attitude of the land and the 

 probable rainfall, as weU as any periodicity in 

 these conditions, are all reflected in the sedi- 

 ments. Work like that of Vaughan - on the 

 deposits of tlie Florida keys or tliat of Drew ^ 

 on the part played by denitrifying bacteria in 

 the formation of limestones enable a careful 

 paleobotanist to determine in a measm'e the 

 character of the flora that clothed the marginal 

 lands. In work on deposits that teem with 

 the remains of marine life, as do many of the 

 Tertiary formations of southeastern North 

 Aiiierica, it is possible to arrive at very close 

 approximations of the temperatiu-es of the 

 coastal waters. It may be safely assumed that 

 boreal or temperate floras did not flourish in 

 proximity to tropical marine faunas and that 

 plants reflected their environment in the past 

 as in the present. 



1 Rock, J. X**., The indigenous trees of tile Hawaiian Islands, Uonolulu, 

 1913. 



2 Vaughan, T. W., Carnegie Inst. Washington Pub. 133. 1910. 

 ' Drew, (!. II., Carnegie Inst. Washington Year Book 10, 1911 



