BULLETIN 231] 



WALNUT CULTURE IN CALIFORNIA. 



361 



tree one year old that had been cut off. The bark, however, was still 

 green and had not dried out at the time of the experiment. 



Series 2. Pieces of the atomized bark were then cut out from time 

 to time and dropped into the test tubes of nutrient media, in the same 

 way that cover glasses were used in the other desiccation experiments. 



SERIES I. 



Number days drying. 



Number tubes. 



Positive. 



Negative. 



SERIES II. 



Growths in the inoculated tubes were plated out and transfers of 

 yellow colonies were made to potato cylinders. The characteristic 

 growth on this medium was taken to be conclusive evidence that the 

 growth was that of the walnut bacteriosis organism. 



ACTION OF GERMICIDES ON THE WALNUT ORGANISM. 



Considerable work has been done in experimenting upon the effective- 

 ness of various germicides in killing the walnut organism. Copper 

 sulphate, mercuric chloride, formalin, potassium permanganate and 

 sodium benzoate were used in this work. 



Method. The following method was employed in testing the killing 

 of organism : 



A pure culture of the walnut blight organism was grown for twenty 

 to forty-eight hours in Dunham solution. The culture tubes at this time 

 were considerably clouded with growth. Then three loopfuls of the 

 culture were transferred with a 2 mm. loop to tubes containing the 

 germicide under experimentation. The germicide was always made up 

 with distilled water and of several different strengths. In each tube 

 there was a definite amount of the germicide, either 5 or 10 c.c. In all 

 cases, except formalin, the tubes were sterilized on three successive days 

 for twenty minutes. 



Copper Sulphate. In this experiment the commercial copper sulphate 

 was used with distilled water. The following strengths were tested : 

 1/10 per cent, 1/100 per cent, 1/500 per cent, 1/1000 per cent, 

 1/2500 per cent, 1/5000 per cent. 



