REPORT ON FORESTS. 193 



environment may be unfavorable for other species. Thus, to 

 again refer to the case of Pinus rigida, while it exists in parts 

 of the sand barrens of Ocean, Burlington and Atlantic counties, 

 almost to the exclusion of all other trees, it is stunted and con- 

 picuously less vigorous in appearance as a whole than where it 

 occurs as scattering groves or individuals in richer soil further 

 north. The natural inference is that it would exist to better 

 advantage in a different soil, but that other, more agressive 

 species, higher in the biologic scale, are able to seize upon and 

 hold such soils against it, and that it exists in the pine barrens 

 largely by reason of freedom from competition. This inference 

 is further strengthened if we consider its wide geographic range, 

 as previously noted, which includes a great diversity of soil and 

 climate. 



The relation between these existing facts and the events 

 which preceded them will be discussed in the next section. 



IL Historical Development* 



PRELIMINARY DISCUSSION. 



In tracing the development of plant life through geologic time 

 the fact is well recognized that the flora of Eozoic and Palaeozoic 

 times is not related to our living flora by any closer ties than 

 those of sub-kingdoms or classes. In Mesozoic time generic rela- 

 tionships may be traced, while in Neozoic time many species 

 identical with, or closely related to, living ones, may be identi- 

 fied. 



It is also accepted, as a broad generalization, that biologic 

 development has been synchronous with the stratigraphic 

 sequence, or, in other words, that the older the geologic forma- 

 tion the lower in organization are its accompanying fossils, and 

 conversely that the more recent the geologic formation the higher 

 in the scale of life are its fossils. 



In palseobotany the facts in this latter connection are particu- 

 larly striking and provide us with excellent data from which to 

 draw conclusions. Plant life was evolved into its present status 

 largely through the influence of changes in environment, and 

 changes now under way are modifying it still further. In order 

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