358 F. B. GUTHRIE AND L. COHEN. 



of manganese compounds. Analyses of these soils show 

 that those on which the pines become yellow contain on 

 the average as much as 5'61i of manganese (calculated as 

 Mn 3 4 ) in the surface-soils as against 0'37°/° in the soils 

 producing the healthy pines. In this case it is to be noted 

 that both soils are highly ferruginous, containing over 20°/° 

 ferric oxide, the good soil being of a red colour, while the 

 infertile soils are black. He has shown a further interest- 

 ing point which bears upon the question immediately before 

 us, namely, that on soils containing an intermediate pro- 

 portion of manganese, (l # 36 /° Mn 3 4 ), the pines become 

 distinctly yellow during the winter months, but sometimes 

 recover completely with the return of the warm weather. 



Although the quantities of manganese found in the poor 

 soil examined by us is not nearly so great as that in the 

 black Hawaiian soils (containing only '245°/° calculated as 

 Mn 3 04.), yet it is possible that the peculiarity noticed in 

 this soil, that the grass dies down in the winter, is due to 

 the same cause, namely, the presence of an amount of 

 manganese not sufficient to kill the plants when growing 

 vigorously, but sufficient to affect them when in a less 

 vigorous state of growth. Aso 1 has also pointed out that 

 the toxic effect of manganese salts on wheat and barley is 

 greatest in the cold weather, the plants recovering them- 

 selves completely with the return of warm weather. 



That the cause of the failure of the grass in these patches 

 is due to the presence of manganese is only put forward as 

 a suggestion. It is to be noted that the Dubbo soil is not 

 particularly rich in iron, and that the soils do not differ in 

 colour, both being of a brownish colour becoming red on 

 ignition. The peculiar fact that the grass showed no sign 

 of the effect of the poison for the first three years is also 



1 Bulletin, College of Agriculture, Tokio Imperial University 5, No. 2, 

 p. 177. 



