1920.] NATUKAL SCIENCES OF PHILADELPHIA. 95 



or of lenses of calcareous clay, the acidity of the soils is markedly 

 diminished. These areas, mostly only a few meters in diameter, 

 and more or less circular in outline, are scattered through the woods, 

 forming in a sense oases in the desert; with the exception of Chima- 

 phila maculata, the Ericaceae appear to avoid them. Wherever 

 Asplenium showed up in the forest floor, — and it was very prominent, 

 the fronds attaining lengths of as much as 40 cm., — tests invariably 

 showed the area it occupied to be subacid or circumneutral in reac- 

 tion. Presumably the spores of this fern are killed when they fall 

 into the more acid soils of the region. 



The Aquilegia, together with a few plants of Asplenium, was 

 observed in quite a different habitat, namely, on the steep banks 

 of the Indian River. The low acidities observed were in this case 

 obviously connected with, the fact that the plant roots entered 

 directly the lower layers of the soil, which are everywhere less acid 

 than the surface portions. Epigaea repeals was also found to grow 

 on the same banks, but its roots do not enter the low acid sands to 

 any extent, being instead imbedded in superficial peaty material 

 wdth the usual mediacid reaction. 



Another type of relationship is shown by Yucca filamentosa, the 

 optimum for which appears to lie at specific acidity 30. This plant 

 grows, apparently as a native and not an escape, in large patches 

 in the more open pine woods, where the surface soil is upland peat 

 with mediacid reaction. It has, however, an erect underground 

 stem 25 or more cm. long, at the base of which is a cluster of tuber- 

 ous roots, with fibrous ones extending downward from them. As 

 far as its root system is concerned, therefore, this species is growdng 

 not in highly acid, but in subacid soils. 



Region East of Washington, D. C. 



The region east of Washington is so similar to the New Jersey 

 and Delaware areas already discussed that little need be said about 

 it at this point. Plant distribution is elaborately treated in a 

 recent publication.^ The magnolia bogs as therein defined are 

 dominantly mediacid in reaction, and the upland peat of the dry 

 surrounding hillsides attains the same acidity, so that Ericaceae 

 and their usual associates abound in both habitats. Subacid and 

 rarely minimacid soils occur on banks and locally through the woods, 

 and support a few plants which can not stand the higher acidities. 



^McAtee, W. L. A sketch of the Natural History of the District of Columbia, 

 Bull. Biol. Soc. Wash., 1: 142 pp., 1918. 



