1920.] NATURAL SCIENCES OF PHILADELPHIA 87 



nassia caroliniana, Rhamnus almjolia, and an appalling abundance 

 of Rhus vernix and R. toxicodendron. All these but the last two 

 seem quite absent from the Dover swamps. 



The pitcher plant, Sarracenia purpurea, grows in both swamps, 

 in the Green Pond one only in the moss hummocks; and the water 

 in the ''pitchers" shows some peculiar reactions. The writer has 

 tested the water held by this plant in many localities, and has found 

 it to be usually mediacid, or subacid, the acidity being no doubt due 

 chiefly to dissolved carbon dioxide. In the Green Pond swamp, 

 however, the water in the pitchers was found to be minimacid, neu- 

 tral and even minimalkaline. It is possible that the plant may be 

 able to absorb lime from the moss in which it is rooted, and excrete 

 it into the pitcher liquid. It seems more probable, however, that 

 lime is absorbed by the roots of the larch trees, (which are abundant 

 in the Green Pond Swamps, though rare at Dover,) and of other 

 shrubs and trees growing in the alkaline water; and that this lime, 

 excreted upon the leaves of these trees, is washed off by the rain 

 and thus gets into the upturned pitchers. 



. Mountain Ridges in the Central Counties of Pennsylvania. 



Tests have been made of the soils of Ericaceae and other plants 

 at a number of places in the mountains of Pennsylvania, from Scran- 

 ton on the northeast to Williamsport on the northwest, and from 

 Bethlehem on the southeast to Mont Alto on the southwest. A 

 few of the most interesting localities will be described here in some 

 detail, starting at the northeast end. 



The most prominent ridges in the region are underlain by sand- 

 stone rocks, and the soils they yield are mostly mediacid to sub- 

 acid. Lower elevations are occupied by shale rocks, which may also 

 give rise to strongly acid soils. Under circumstances where accumu- 

 lation of vegetable matter is prevented, the reactions connected with 

 both these rock types may be minimacid to neutral. As an illus- 

 tration, it may be noted that the fern Cryptogramma stelleri (Pellaea 

 gracilis) usually described in manuals as a limestone species, was 

 collected at Lincoln Falls, Sullivan County, miles away from any 

 limestone. The rock is a red shale (of Devonian age) and the water 

 oozing from it is neutral in reaction. 



At South Stroudsburg the Rhododendron nursery of W. K. Labar 

 was visited, and the methods of growing ericaceous plants there 

 were kindly demonstrated by Mr. John van Kleef, the resident 

 manager. The natural soil of this place is a calcareous glacial 



