90 



I gm. Sodium asparaginate. 

 1 gm. Dextrose. 

 .2 gm. Magnesium sulphate. 



1.5 gm. (NH4H2PO4) ammonium Diphosphate. 

 . 1 gm. Calcium chloride. 

 . 1 gm. Potassium chloride. 

 Trace Ferrous chloride. 

 1,000 cc. Distilled water. 



Soil Extract (Unheated). 



15 grams of best agar dissolved in 1,000 cc. of solution made us follows: 



Two kilos of the brown loam soil were placed in a glass bottle, and 5 



liters of distilled water added, the bottle was shaken at intervals and al end 



of 16 hours the mixture was filtered. One thousand cc. of the filtrate was 



used in place of distilled water in making up this media. 



Soil Extract (Autoclaved). 



Fifteen grams ot best agar dissolved in 1,000 cc. of solution made the 

 same as the soil extract (unheated), except that the two kilos of soil were 

 wet well and heated under 25 lbs. pressure in the autoclave for three hours. 



Soil and agar, leaf extract and agar, and wheat straw extract. 



These three media were made as follows: To 15 gms. of the best agar 

 were added 10 gms. of the material desired and 1,000 cc. distilled water. 

 The mixture was heated in a double boiler until the agar was dissolved. 

 After making up to volume the media was filtered and tubed. 



Other Media. 



To 15 gms. of best agar was added 1 gm. per liter of chemicals appearing 

 as part of the name of the media and 1,000 cc. of distilled water. 



Figure 1 expresses graphically the acidity of the various media. The 

 procedure in titrating was as follows: To about 125 cc. of distilled water 

 that has been boiling about 3 minutes in a Jena erlenmeyer flask was added 

 50 cc. of the media by means of a tall 50 cc. graduate (of small cross-section). 

 Two drops of phenolpthalein solution was added and titration made with 

 tenth normal sodium hydroxide. The only media neutralized at all was II. J. 

 Conn's sodium asparaginate agar, and this was done with half normal soda, 

 using a pipette graduated to one-twentieth of a cc. 



