PLATE VI. 



Fig, 1. — Peas grown in extract of soil from plol 32, Pennsyl- 

 vania rotation experiments. 



(1) Extract plot 32, original condition. 



(2) Extract plot 32, incubated withou; fertilizer. 



(3) As (2), plus 1 cc N/1 KOH. 



(4) As (2), plus 2 cc N/1 KOH. 



(5) Extract plot 32, incubated with ammonium sulphate. 



(6) As (5), plus 2 cc N/1 KOH. 



(7) As (5), plus 4 cc N/1 KOH. 



(8) As (5), plus 1 gram CaCOo. 



(9) As (5), plus 1 gram CaCOo,''plus COo. 



(10) Extract plot 32, second leaching. 



Fig. 2.— Cultures (5) and (7), fig. 1. 



On left, untreated extract. 



On right, extract plus 4 ccN/1 KOH per 500 cc extract. Note 

 the extensive root development, and the precipitated manganese 

 in the bottom of the tumbler. 



