2 28 Mineral Nutrition of Fungi [jan. 



a slight increase was observed in the weight of the fungus, corre- 

 sponding to the weight of the calcium used. Of loo mg. of calcium 

 in 250 c.c. of medium, 73.4 mg. of calcium were recovered from the 

 mycelium. Smaller doses were recovered completely. In a later 

 paper Robert-^ showed that the calcium was fixed in the form of 

 Oxalate. Analyses of m3rcelium grown on different amounts of 

 calcium showed calcium and oxalic acid to be present in molecular 

 proportions. This suggests the formations of raphides in higher 

 plants, where calcium Oxalate may be observed in the form of 

 crystals. Although calcium is fixed by the fungus, its presence is 

 by no means necessary. 



There is still a question as to how sharp a distinction can be 

 drawn between nutrients and catalysers. Raulin's medium prob- 

 ably contains other catalysers besides the zinc and iron. The 

 hydrogen ion furnished by the tartaric acid undoubtedly accelerates 

 the growth of the fungus, since the latter does not thrive nearly so 

 well in a neutral synthetic medium. The purpose of adding the 

 acid was originally to aid in sterilization and prevent contamination 

 with bacteria and yeasts, since sterilization of liquids at tempera- 

 tures above their boiling points was not practised in Raulin's time. 

 Buromsky regards the nitrate ion of Raulin's medium as both 

 catalyser and nutrient. He found the medium to be less efficient 

 when ammonium sulphate was substituted for the nitrate. 



Many important problems regarding the mineral nutrition of 

 lower fungi still await investigation. 



28 Robert: Compt. rend., 154, 1308-10 (1912). 



