51 



spores are soon formed. A similar effect on oats was observed by 

 SchneidewindJ Of all nitrates tested, magnesium nitrate yielded the 

 largest grain production. 



NECESSITY OF MAGNESIUM SALTS FOR FUNGI. 



Magnesium salts are also indispensable for fungi, but an exceedingly 

 small amount will suffice when the nourishing solution has an acid 

 reaction. In fact, even traces of magnesia taken up from glass vessels, 

 if the latter are not made of the most resistant material, will suffice 

 for growth. Friinkel denies the necessity of magnesia for certain kinds 

 of bacteria — ^ Bacteritim coli, B. pyocyaneus Friedl., and other bacteria 

 having been cultivated by him in solutions of aspartate or lactate of 

 ammonia in absence of magnesium salts. However, a suspicion as to 

 the absolute purity of his materials may be justly entertained. 



How small a quantity may suffice for mold fungi is shown by the fol- 

 lowing observation: The writer prepared a nourishing solution con- 

 taining 2 per cent of ammonium acetate, 0.04 per cent monopotassium 

 phosphate, and 0.02 per cent potassium sulphate and infected the solu- 

 tion, which was made with absolutely pure materials, with spores of 

 Penicillimn, but obtained no growth, owing to the absence of magnesia. 

 He then added 0.0003 per cent of magnesium sulphate, and soon a con- 

 siderable development of mycelium took place, its weight finally becom- 

 ing very nearly the same as that in the control flask containing 0.1 per 

 cent of magnesium sulphate.^ The only difference observed between 

 the two cases was that in the former flask spores were entirely absent, 

 while in the latter they were i)resent in great numbers. 



Giinther'' inferred from his experiments that the limit of sensibility 

 of the fungus Bhizopus to magnesium sulphate is 0.005 milligram. 

 From such experiments it seems very probable that in those made by 

 Frankel with bacteria traces of magnesia were present as impurities 

 in some of the compounds used. 



Molisch has observed, and his observations have been confirmed by 

 the writer, that spores of Penicillium do not even germinate in culture 

 solutions entirely free from magnesia and containing ammonium acetate 

 as the only organic nutrient — a fact which appears very strange, as there 

 is certainly stored up in the spores a sufficient amount of magnesium 

 phosphate to make germination and even some further development 

 possible, and indeed magnesia has been found repeatedly in the ash 

 of various fungi. The writer has cultivated Penicillium in a solution 

 containing peptone, tartaric acid, monopotassium phosphate, and 0.1 

 I)er cent magnesium sulphate, and has convinced himself of the 



1 Journ. f. Landw., 1898, Vol. XLVI, p. 1. 



2 Centralbl. f. Bakt., Vol. XVII, p. 32. 



•' Experiments with Penicillmm succeed best in moderately acid solutions, 

 tLoc. cit. (p. 25). 



