84 Effect of Manganese Compounds 



as much as •254 % MiijOg was found in that from the dead patches. As 

 no other differences were found it was argued that the manganese> 

 present in such large quantities, acted as a toxic agent and killed off the 

 grass. Other instances of manganese poisoning in which wheat and 

 bariey were affected are quoted by these authors, the analytical results 

 indicating that possibly barley is able to withstand without injury a 

 greater quantity of manganese compounds in the soil than is wheat. 



2. Effect of manganese compounds on germination. 



Nazari (1910) rolled wheat grains in a paste of manganese dioxide, 

 iron sesquioxide (both with and without organic matter), and in what he 

 terms " artificial oxydases." The seeds rolled in the last-named showed 

 the greatest energy in germination, while those with manganese gave 

 an appreciable acceleration. The presence of organic matter decreased 

 the action of manganese. The plants from the manganese seedlings gave 

 an increased yield in both' straw and grain, while those treated with 

 sesquioxide of iron showed no gain over the check plants. 



The Hills Experiments yielded some information as to the differing 

 effects of various compounds of manganese on germination. With wheat 

 plants in pot experiments manganese oxide (MnOa) distinctly retarded 

 germination when applied at the rate of 2 cwt. per acre. With barley 

 MnOa, manganese carbonate and sulphate all retarded germination, while 

 with the iodide 50 % of the seeds were entirely prevented from germi- 

 nating. 



3. Does manganese stimulate higher plants ? 



With manganese the evidence in favour of stimulation is more 

 weighty than with such poisons as copper, zinc and arsenic, and the 

 literature on the subject is correspondingly plentiful. 



(a) Stimulation in water cultures. 



While Aso (1902) asserted that plants can develope normally in 

 water cultures in the absence of any trace of manganese, he further 

 stated that manganese compounds exercise both an injurious and a 

 stimulant action on plants. With increasing dilution of the compound 

 the deleterious action diminishes, while the stimulant action increases, 

 and a dilution can be reached in which only the favourable influence 

 of the manganese becomes obvious. The addition of -002 % manganese 

 sulphate ( = 1/60,000) to culture solutions stimulated radish, barley, 



