MAGNESIUM SALTS. 59 



The average proportion of magnesia in starchy seeds to that in oily 

 seeds, therefore, is as 2 to 5. 



It may furthermore be pointed out that fungi grown in culture solu- 

 tions containing only traces of magnesia form no spores. Spores, how- 

 ever, contain lecithin, and in all probability relatively large amounts of 

 nucleoprotein. Here the importance of magnesia can be readily dem- 

 onstrated by increasing its amount in the culture solution, after which 

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

 Schneidewind/' Of all nitrates tested, magnesium nitrate yielded the 

 largest grain production. s 



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. Frankel denies the necessity of magnesia for certain kinds 

 of bacteria^ — Bacterium, coli, B.pyocy emeus 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 of magnesium salts may suffice for mold f ungf 

 is shown by the following observation: The writer prepared a nour- 

 ishing solution containing 2 per cent of ammonium acetate, 0.04 per 

 cent monopotassium phosphate, and 0.02 per cent potassium sulphate 

 and infected the solution, which was made with absolutely pure mate- 

 rials, with a few spores of Penicillium , but obtained no growth, owing 

 to the absence of magnesia. He then added 0.0003 per cent of mag- 

 nesium sulphate, and soon a considerable development of mycelium 

 took place, its weight finally becoming very nearly the same as that in 

 the control flask containing 0.1 per cent of magnesium sulphate. c The 

 only difference observed between the two cases was that in the former 

 flask spores were entirely absent, while in the latter they were abund- 

 antly formed. 



Giinther d inferred from his experiments that the limit of sensibility 

 of the fungus Rhizopus 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/ 



aJourn. f. Landw., 1898, Vol. XL VI, p. 1. 

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



c Experiments with Penicillium succeed best in moderately acid solutions. 

 ^Seep. 33. 



e This applies also to the belief of Thumm that magnesium can be replaced by 

 calcium in the culture of certain bacteria, as B. pyocyaneus. 



