207 KNOP, W.-Uber die Ernahrung der Pflanzen durch 

 wassnge Losungen bei Ausschluss des Boden. 

 Landw. Vers. Stat, Bd. II, S. 73. 

 To 1 1. water was added: 



•00s .03 .05 gr. S. of I. and 

 .005 .03 .05 gr. Ferrous Phosphate. 

 The plants were killed by the solution 0.05 gr. of ferrous salt, 

 and this probably due to the absorption of oxygen. 



Used mixture of ferric phosphate, basic ferric sulphate and 

 basic ferric acetate. 



Ferric salts not poisonous. 



208 KNOP, ( ).— Kreislauf d. Stoffes (1868), S. 614. 



Also Ber. d. Sachs. Gesell. d. Wissensch. zu Leipsig, Bd. 25 



(1869), S. 8. 



Use of potassium ferrocyanide. 



209 KNOP, W. — Quantitative Arbeiten uber den Ernahrungs 

 process der Pflanzen. 



Landw. Vers. Stat., Bd. V, S. 99. 



An answer to the question — -"Is iron necessary to the nutrition 

 of plants?" Found that a small quantity of iron appears to be 

 necessary for the continuation of plant growth. 



210 KONIG, J. — Mittheilung uber die, Veranderungen von 

 Kochsalz, u. Schwefelsaurem Zinklosungen bei 

 Rieselversuchen. 



Landw. Jahrb. Bd. XII, (1883), S. 37. 



211 KONIG, J. — Nachtrag zu vorstehenden Versuchen iiber 

 den schadlichen Einfluss von Kochsalz und zink- 

 haltigem Wasser auf Boden und Pflanzen. 



Landw. Jah'rb., Bd. 12 (1883), S. 837. 



S. of I. on filtering into soil breaks up into basic ferric sulphate 

 and free sulphuric acid, which latter acts on materials in the 

 soil, causing them to dissolve. Action for most part is on calcium 

 and potassium compounds. The soil may become contaminated 

 by large quantities of hydrated ferric compounds, the pores stop- 

 ped, the supply of oxygen cut off, in which case a gradual sour- 

 ing of the soil may result. 



