igo GEOLOGICAI^ SURVEY OF NEW JERSEY. 



where it occurs close to the edge of the Triassic border, but has 

 not been recorded beyond. 



Quercus nigra. Practically the same range as the latter. 



If the above defined areas of distribution and lines of limita- 

 tion be studied it will at once be apparent that they are not due 

 to climatic conditions. In the case of ChamcBcyparis we have 

 a species which exists as far north as Massachusetts and as far 

 south as Florida, while Pinus rigida is known from Canada to 

 Georgia — their occurrence north of the coniferous zone being 

 apparently largely due to locally favorable physiographic con- 

 ditions. 



Considering other species we may even eliminate physio- 

 graphic conditions as a cause of distribution, as, for example, 

 Quercus Phellos and Q. nigra.^ which extend northward in the 

 eastern part of the state as far as Perth Amboy, but in the 

 western part are not known north of Trenton. A line drawn 

 between these two localities defines their limit of distribution. 

 The topographic features for a large part of the distance along 

 both sides of this line are practically identical, and yet neither 

 of the species crosses it. The fact which is at once apparent, 

 however, is that this line is coincident with the line which' 

 separates the Cretaceous and Triassic oiitcrops, and the rational 

 inference is that this feature, the geologic, is the important one 

 to be studied. 



In the instances quoted the coincidence between the geologic 

 features and the areas of distribution and lines of limitation are 

 more striking than in most cases, as they were chosen specially 

 for that purpose, but there is no doubt that a careful tabulation 

 of similar facts in regard to other species would be exceedingly 

 interesting and significant. 



DISCUSSION OF THE FACTS. 



If the foregoing facts be carefully considered, one feature in 

 connection with them will at once attract attention by reason of 

 its constant reiteration. This is the influence apparently exerted 

 by certain geologic formations upon the distribution of certain 

 classes or species of trees, or, for the sake of argument, the 

 coincidence which apparently exists between certain geologic 



