1920.] NATURAL SCIENCES OF PHILADELPHIA. 103 



The optimum soil reaction of this species is probably mediacid. 

 The lowest acidities tabulated, marked o, represent an occurrence 

 south of Willoughby Lake, Vt., where the plant grows at the margin 

 of an alkaline water pond, and its roots push out as far as material 

 of this acidity. It is also grown in nurseries in dry sandy soil be- 

 tween subacid and minimacid in reaction. 



Oxydendrum arboreum (L.) DeCandoUe. 



Habitat. — Dry upland peat. 



As observed in southern Virginia, this plant grows in woods 

 where the surface soil is mediacid, but its roots usually extend down 

 into material of subacid reaction. 



Epigaea repens L. 



Habitat.- — Dry upland peat and occasionally moist peat. 



Acidity. — 



5+ X 



4 X 



3 X 



2 X 



1 



300 100 30 10 3 1 



The optimum soil reaction of this species is probably subacid, 

 although it is fairly common in mediacid soils as well. The least 

 acid reactions tabulated were observed in upland peats near Wash- 

 ington, D. C. The most heavily fruiting plants and the most 

 numerous seedlings have been found in subacid soils. 



Gaultheria procumbens L. 



Habitat. — Dry and moist upland peat, and wet sphagnum peat. 



Acidity.— 



5+ X 



4 



3 



2 XX 



1 o 



300 100 30 10 3 1 



The optimum soil reaction of this species is probably mediacid, 

 although it is fairly common in subacid soils as well. The least 

 acid reaction (o) was observed in upland peat on calcareous glacial 

 drift near Fairlee, Vt. 



