1920.] NATURAL SCIENCES OF PHILADELPHIA. 97 



Clethra alnifolia L. 



Habitat. — Wet sphagnum peat and occasionally dry upland peat 

 at swamp margins. 



The optimum soil reaction for this species is obviously mediacid. 

 The lower values sometimes observed represent places where the 

 plant pushes out from its usual swamp habitat into dry sandy woods. 

 The n in the table refers to a test of sandy soil in Gillett's nursery 

 at Southwick, Massachusetts, and is introduced to show that this 

 plant can be grown under cultivation in a soil of somewhat lower 

 initial acidity than it appears to occupy in nature. 



Pyrola americana Sweet. 



Habitat. — Dry upland peat and occasionally moist peat at swamp 

 margins. 



Acidity. — 



5+ X 



4 



3 X 

 2' 



1 X X X 



300 100 30 10 3 1 



The optimum soil reaction for this species is subacid. The most 

 acid reaction tabulated was observed in moist peat at the margin 

 of a swamp north of Dover, N. J. The least acid was noted in up- 

 land peat on glacial drift overlying limestone in the Lehigh Valley 

 west of AUentown, Pa. 



Pyrola elliptica Nuttall. ' 



Habitat. — Dry and occasionally moist upland peat. 



Acidity. — 



5+ X 



4 X 



3 o 



2 o o 

 1 o 



300 100 30 10 3 1 



'In the succeeding tables these names are omitted for brevity. Their use in 

 the text will be understood to imply the same degree of acidity here indicated. 



