86 RESEARCHES ON FUNGI 



in a mortar and thoroughly mixed with 50 c.c. of distilled water ; 

 and the mixture was allowed to stand for 10 minutes. The extract 

 was then filtered off and placed in a flask with a cotton-wool plug 

 and sterilised by heating in a steam steriliser at a temperature of 

 100° C. for one hour. 



(3) The bean decoction was made from fresh String Beans 

 {Phaseolus multiflorus). The bean pods were crushed in a mortar 

 and mixed with about their own weight of distilled water. After 

 filtering, the filtrate was placed in a flask with a cotton-wool plug 

 and sterilised by heating for 45 minutes in a steam steriliser at a 

 temperature of 100° C. 



(4) Pollock's formula ^ for his optimum culture medium for a 

 soil fungus is given in gram-molecules as follows : saccharose f M., 

 calcium nitrate -^\-^ M., monopotassium phosphate yo-too ^-^ ^^^ 

 magnesium sulphate Y^mS ^• 



(5) The nutrient gelatine had the following composition : 

 distilled water 500 c.c, gelatine 50 gm., dextrose 5 gm., peptone 

 5 gm., Liebig's meat-extract 1-5 gm., and sodium chloride 2-5 gm. 

 The mixture was neutralised with sodium hydroxide, cleared with 

 two eggs, and filtered through cotton-wool. The medium was 

 then placed in a flask with a cotton-wool plug and steriUsed by 

 heating at a temperature of 100° C. twice, the first time for 1 hour 

 and the second time, 48 hours later, for 45 minutes. 



In making the hanging-drop cultures, all the usual precautions 

 were taken to prevent accidental infection by bacteria, yeasts, or 

 moulds. The apparatus of the glass cells was arranged in most of 

 the experiments in the manner recommended by B. M. Duggar.^ 

 A Petri dish was taken and a piece of filter paper was fitted within 

 its base. In this piece of filter paper were made ten circular holes, 

 each one with a diameter just a little larger than that of the glass 

 rings to be employed. Ten glass rings were then set in the ten 

 holes, a cover-glass was laid on each ring, and the cover of the Petri 

 dish applied. The whole was then sterilised in a hot-air oven at 

 a temperature of 160° C. for one hour. A drop of the culture medium 



1 J. B. Pollock, "An optimum culture medium for a soil fungus," Science, 

 N.S., vol. 37, 1913, pp. 286-287. 



2 B. M. Duggar, Fungus Diseases of Plants, New York, 1909, pp. 57-59. 



