26o 



K. NEC A MI ; OX THE PHYSIOLOGICAL ACTION 



gypsum solution. This solution was renewed every second day 

 as an oxidation to sulphate takes place rather quickly. For 

 control I prepared a corresponding solution of sodium sulphate 

 mixed with an equal volume of saturated gypsum solution. Bar- 

 ley plants, however, showed in these solutions after 7 days no 

 distinct signs of disease. 



As I surmised that the oxidation of sulphite to sulphate might 

 have been the cause of this result, I used in my next experiment 

 a solution of double the former concentration, mixed with gypsum 

 solution as above, and compared its effect with that of sodium 

 sulphate under equal conditions and also with that of plain water. 

 The sulphite solution was here renewed every day, as I had ob- 

 served that the oxidation to sulphate proceeded much more 

 quickly than I had surmised. The experiment was commenced 

 Avith onions and barley plants on the i6th March. 



Temperature : min. 8°C, max. i6°C. 



I. Experiments ivitJi WJiolc Plants. 



Experiment intli Onions : 



After two days a poisonous effect of the sulphite was plainly 

 seen in one of the stems, which dried up on the tip and lost its 

 turgor ; while all the control plants remained healthy. 



On the fifth day the plants in the sulphite solution were dead, 

 except the youngest branches which had still some turgor. Two 

 days later all the parts of these plants were killed, while the con- 

 trol plants looked still well except that the tips of the leaves 

 were drying up. 



Experiment ivitJi Barley : 



The plants kept in the sulphite solution showed after two 

 days a poisonous action to a small extent, withering near the tips 

 of the leaves, but on the fifth day some of the large leaves had 

 completely dried up ; other leaves were also damaged, their upper 

 parts having turned yellow, while the lower parts still appeared 



