186 GEOLOGICAL SURVEY OF NEW JERSEY. 



being more or less scattered, usually following minor surface 

 conditions, such as water-courses, swamps, fence lines, &c. 



Doubtless in certain sections other species than those above 

 listed would appear equally important as elements in the flora, 

 but those enumerated will give a fair idea of the arboreal 

 features as a whole. If a complete census of all the species 

 which inhabit each zone be made, and studied, it will be found 

 that the deciduous zone contains the greater number and diver- 

 sity, and that, as a rule, they are well mixed ; no one species 

 forming the bulk of the forest over any considerable area. In 

 the coniferous zone, on the contrary, the monotonous uniformity 

 of the forests, due to extensive aggregations of a few predominant 

 species, is often conspicuous over hundreds of square miles. In 

 the latter zone, for example, Pinus rigida is not only the pre- 

 dominant but almost the exclusive species, over large areas, but 

 no such example can be quoted in regard to any one species in 

 the deciduous zone. This species also occurs in several scattered 

 groups northward in the state, but not in sufficient numbers to 

 form forests or to be classed as characteristic of the deciduous 

 zone. 



If now the geology and topography of each zone be considered 

 it may be seen that the southern limit of the deciduous zone is 

 quite sharply coterminous with the southern edge of the Triassic 

 outcrop, and that it extends unrestricted in all other directions 

 up to and beyond the state line and that its geologic and topo- 

 graphic features are exceedingly varied. The coniferous zone, 

 on the contrary, is coterminous along its northern border with 

 the northern border of the Tertiary sands and gravels and pre- 

 sents but little diversity either in its geology or topography, 

 except for the fringe of sand beaches and salt marshes at tide- 

 water, by which it is limited in the east and south. Its area is 

 restricted by these barriers in these directions, but it extends 

 beyond the boundary of the state south west wardly. The tension 

 zone, which includes practically the whole of the Cretaceous 

 plastic clays and the Cretaceous and Tertiary clay marls and 

 marls, is intermediate, geographically and in its geologic and 

 topographic features, between the other two. 



The above-mentioned facts may be observed to advantage in a 

 number of critical localities, as, for example, in the vicinity of 



