356 F. B. GUTHRIE AND L. COHEN. 



A great number of experiments have been made of recent 

 years, both in pots and in the field, to test the eflect of 

 such substances as salts of manganese, zinc, etc., on the 

 growth of plants, particularly by O.Loewand his co-workers 

 at Tokio, and others. A resume of the work done and 

 references to the original papers will be found in the 

 Annual Reports of the Chemical Society, Vols. i-v. An 

 excellent resume is also given by G. Pollacci. 1 



On the whole, although the results so far obtained can- 

 not be regarded as entirely conclusive, it appears that 

 manganese compounds in the soil in small quantities exert a 

 stimulating eflect on the growth of many crops, but 

 whether that effect is due to the direct action of man- 

 ganese as plant-food or to a secondary action upon other 

 constituents in the soil is not yet satisfactorily determined. 

 Some chemists state that the presence of manganese is 

 necessary to the growth of the plant, and that it is present 

 in minute quantities in all soils. In the particular case of 

 meadow-grass, G. Salomone 2 found that the pasture was 

 greatly improved by the addition of small quantities of 

 sulphate of manganese, 1 grm. of the metal per square 

 metre (about 27 lbs. of sulphate of manganese per acre) 

 produced a more vigorous growth and of a darker green, 

 the yield of hay calculated to the hectare being 760 kilos 

 greater in the case of the plot which had received the 

 manganese than in the other. The effect on other crops 

 of small quantities of manganese will be found by consult- 

 ing the references already referred to. 



Mr. Outhbert Potts of the Hawkesbury Agricultural 

 College has also been conducting experiments in this direc- 

 tion, both in the field and in pots. Mr. Potts has experi- 

 mented with wheat for hay in the field by manuring with 



1 L'Industria Chimica, Anno 9, No. 5, p. 65, March 10th, 1909. 



2 Le Staz. Sper. Agr. Ital... Vol. xl, p. 108. 



