116 PROCEEDINGS OF THE ACADEMY OF [April^ 



region. Because of containing considerable rock-flour, and of not 

 having been long (geologically speaking) subjected to weathering, this 

 formation yields soils relatively high in calcium and potassium 

 salts. The content of calcium carbonate is less, however, than in 

 the Cretaceous, so that acids are not as completely neutralized, and 

 subacid reactions are most characteristic of the areas underlain by 

 the Cape May. 



The soil acidities of the several vegetation-areas are determined 

 by the distribution of these different geological formations in them. 

 In the Marl area — • named after the most characteristic material 

 represented — the salt content averages high and acidity low because 

 the Cretaceous strata outcrop in many places. More or less iso- 

 lated patches of Cape May and of Pensauken deposits occur in the 

 area, and show locally lower salt content and greater acidity. In 

 the Cohansey area Cape May deposits are most widespread, so that 

 the average acidity is moderate; but again isolated patches occur, 

 in this case occupied by Miocene and Pensauken deposits, in which 

 the acidity is high. The Cape May and Pine-barren areas are- 

 occupied essentially by single geological formations, and show the 

 acidities characteristic of these in each case. The peculiar features 

 of the Coastal and Maritime areas have been discussed in the paper 

 above referred to. 



Relation of Soil Acidity to Plant Distribution. 



Tests have been made of the soils surrounding the roots of a number 

 of plants in each of these areas, and as the results obtained have 

 furnished evidence in support of the view that plant distribution is 

 intimately connected with soil acidity, a few typical instances may 

 well be described here. 



The rattlesnake fern, Botrychium virginianum, which in other 

 regions is most frequently found in circumneutral soils, is common 

 in southern New Jersey in the Marl area, and occasional in the 

 Cohansej^ and Cape May areas; it appears to be quite absent, how- 

 ever, from the Pine-barren and Coastal areas. As there is no physi- 

 cal barrier to its spreading into the latter areas, the inference seems 

 justified that when its spores reach these areas their germination is 

 prevented by the high degree of acidity present. By way of con- 

 trast, the curly-grass fern, Schizaea pusilla, is limited to the Pine- 

 barren and Coastal areas, and actual tests of its soils have shown 

 mediacid reaction. Here there seems to exist an inability of the- 

 plant to become established except where the acidity is high. 



