Bui. 227, U. S. Dept. of Agriculture. 



Plate I. 



Toxicity Studies: Apparatus and Petri-Dish Cultures. 



Fig. 1. — Frame for agar and preservative bottles during sterilization. Fig. 2. — Inoculation case, 

 showing water bath on hot plate and other apparatus used. Fig. 3. — Petri-dish culture of 

 Fomes annosus cut into squares ready for transferring to the test plates; platinum needle with 

 flattened tip used in the operation. Figs. 4 to 9. — Petri-dish cultures of Fomes pinicola on 

 different concentrations of coal-tar creosote, grade C, after 5 weeks: 4, Check; 5, on 0.075 per 

 cent; 6, on 0.1 per cent; 7, on 0.125 per cent; 8, on 0.15 per cent; 9, on 0.175 per cent. 



