PLANTS OF SOUTHERN NEW JERSEY. 43 



In plant distribution we have to reckon with other factors in 

 addition to temperature, which are only indirectly instrumental 

 in the distribution of vertebrate animals or are not at all in 

 evidence. 



(i) Soil conditions play a very important part in the distribu- 

 tion of plants, and (2) the past geological changes in the region, 

 which necessarily caused great alterations in the ranges of both 

 animals and plants, have often left their mark in the isolated 

 colonies of plants still found in spots far removed from the 

 present general habitat of the species, while in the case of free 

 moving animals such cases are rare. 



It should also be borne in mind that the life-zones of to-day 

 are not permanently fixed, but are constantly and gradually 

 changing, and oftentimes man accelerates these changes very 

 materially by clearing forests, draining swamps, etc.* 



The flowering and filicoid plants of the New Jersey coastal 

 plain comprise IS73J species. Of this number no less than 807 

 are more or less common in the Piedmont region. They are 

 either of boreal affinities or plants adapted to richer, heavier soil, 

 and have spread southeastward across the fall line into the 

 northern and western portions of the New Jersey coastal plain, 

 where many of them are still rare or only locally common, some 

 of them being restricted to the immediate vicinity of the Dela- 

 ware River. Only 181 of them reach the Pine Barrens, and of 

 these only 80 are at all abundant, these being species of wide 

 range. 



On the other hand, 91 species of austral affinities, which are 

 widely distributed over the coastal plain, occur also more or less 

 abundantly in the Piedmont region northwest of the fall line, 

 though they vary greatly both in abundance and in the extent 

 of their distribution westward. 



The remaining 475 species are restricted to the coastal plain 

 except for sporadic occurrences here and there in the Piedmont 



* Cf. Trotter, Geological and Geographical Relations of the Land Bird, 

 Fauna of Northeastern America. The Auk, 1909, p. 231-233 (especially p. 

 230). 



t The figures given here and beyond vary slightly from the actual number 

 of species in the list, as a few have been added and a few relegated to foot- 

 notes or excluded entirely since this count was made. 



